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Appearance of real linear polymer chains as recorded using an atomic force microscope on surface under liquid medium.
^ It is sometimes interpreted as the temperature above which significant portions of polymer chains are able to slide past each other in response to an applied force.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ A general diagram illustrating this assembly of linear macromolecules, which supports the name chain growth polymers , is presented here.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ At low temperatures, chain transfer reactions are rare in such polymerizations, so the resulting polymers are cleanly linear (unbranched).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Chain contour length for this polymer is ~204 nm; thickness is ~0.4 nm.^ It is also the simplest polymer, consisting of random-length (but generally very long) chains made up of two-carbon units.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

[1]
.A polymer is a large molecule (macromolecule) composed of repeating structural units typically connected by covalent chemical bonds.^ Polymers are complex chemicals with repeating structural units that have covalent chemical bonds.
  • Polymers Information | Business.com 23 January 2010 22:16 UTC www.business.com [Source type: Reference]

^ A polymer that is composed of identical monomeric units (as is polyethylene) is called a homopolymer .
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Though a large variety of synthetic or natural polymers is available in the market, polyethylene (or polythene), polystyrene and polypropylene are some of the popular chemical polymer compounds supplied by the polymer manufacturers.
  • Polymers Information | Business.com 23 January 2010 22:16 UTC www.business.com [Source type: Reference]

.While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties, including properties typically associated with plastics.^ For engineering and business aspects of polymers and plastics, please search Socrates , Stanford’s Library Catalog, or consult with reference staff at the Engineering and Business Libraries.
  • SULAIR: Swain Library: Subject Guides: Polymers 10 January 2010 19:43 UTC library.stanford.edu [Source type: Academic]

^ S. Mississippi ) Rubber Manufacturers Association The Society for Biomaterials Society for the Advancement of Material and Process Engineering (SAMPE) Society of Plastics Engineers The Society of Polymer Science, Japan The Society of Rheology The Society of the Plastics Industry, Inc.
  • SULAIR: Swain Library: Subject Guides: Polymers 10 January 2010 19:43 UTC library.stanford.edu [Source type: Academic]

.Because of the extraordinary range of properties accessible in polymeric materials,[2] they play an essential and ubiquitous role in everyday life[3]—from plastics and elastomers on the one hand to natural biopolymers such as DNA and proteins that are essential for life on the other.^ Polymeric materials are often of organic origin and consists mainly of light elements such as carbon and hydrogen.
  • Plastics & Polymers | PANalytical 23 January 2010 22:16 UTC www.panalytical.com [Source type: Academic]

^ For X-ray diffraction experiments the composition of light elements of plastics means that they have a low absorption of X-rays and thus a high penetration depth into the material investigated.
  • Plastics & Polymers | PANalytical 23 January 2010 22:16 UTC www.panalytical.com [Source type: Academic]

^ In the last decades, polymeric materials have found their way from the research lab to virtually any application of modern materials, ranging from medical to automotive and from construction to children's toys and packaging.
  • Plastics & Polymers | PANalytical 23 January 2010 22:16 UTC www.panalytical.com [Source type: Academic]

A simple example is polyethylene, whose repeating unit is based on ethylene (IUPAC name ethene) monomer. .Most commonly, as in this example, the continuously linked backbone of a polymer used for the preparation of plastics consists mainly of carbon atoms.^ Examples of blades used for polymer clay.

^ Polymeric materials are often of organic origin and consists mainly of light elements such as carbon and hydrogen.
  • Plastics & Polymers | PANalytical 23 January 2010 22:16 UTC www.panalytical.com [Source type: Academic]

^ Wool, cotton, silk, wood and leather are examples of natural polymers that have been known and used since ancient times.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.However, other structures do exist; for example, elements such as silicon form familiar materials such as silicones, examples being silly putty and waterproof plumbing sealant.^ Silicones can be made in a wide variety of forms; those having lower molecular weights are liquids, while the more highly polymerized materials are rubbery solids.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Open burning of polymeric materials containing chlorine (polyvinyl chloride, for example) is known to release compounds such as dioxins that persist in the environment.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Such carbons (and the groups attached to them) are said to be chiral , and can exist in two different three-dimensional forms known as enantiomers .
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.The backbone of DNA is in fact based on a phosphodiester bond, and repeating units of polysaccharides (e.g.^ Polymers are complex chemicals with repeating structural units that have covalent chemical bonds.
  • Polymers Information | Business.com 23 January 2010 22:16 UTC www.business.com [Source type: Reference]

.cellulose) are joined together by glycosidic bonds via oxygen atoms.^ The now-empty bonding positions on the two monomers can then join together .
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Notice that the two copolymer sub-units are held together by peptide bonds, the same kinds that join amino acids into proteins.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.Natural polymeric materials such as shellac, amber, and natural rubber have been in use for centuries.^ What are some of the problems connected with recycling or re-use of polymeric materials?
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Raw natural rubber tends to be sticky when warm and brittle when cold, so it was little more than a novelty material when first introduced to Europe around 1770.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ By itself it is quite rigid and used in construction materials such as pipes, house siding, flooring.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.Biopolymers such as proteins and nucleic acids play crucial roles in biological processes.^ In this survey we will look at only those that have major industrial uses, so we will not be discussing the very important biopolymers proteins and nucleic acids .
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ This group includes biopolymers such as proteins and carbohydrates that are constituents of all living organisms.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Synthetic rubbers played a crucial role in World War II: more .
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.A variety of other natural polymers exist, such as cellulose, which is the main constituent of wood and paper.^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Wool, cotton, silk, wood and leather are examples of natural polymers that have been known and used since ancient times.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Fax: +33 329 296 138 Website: http://www.enstib.uhp-nancy.fr E-Mail: Interests: polycondensation; resins; adhesives; thermosetting polymers for adhesives; natural polymers for industrial use; fibrous and wood composites; polymeric wood constituents (cellulose, lignin, tannins) .
  • Editors - MDPI 23 January 2010 22:16 UTC www.mdpi.com [Source type: Academic]

.The list of synthetic polymers includes synthetic rubber, Bakelite, neoprene, nylon, PVC, polystyrene, polyethylene, polypropylene, polyacrylonitrile, PVB, silicone, and many more.^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Natural rubber continues to have a large market despite the many forms of synthetic rubber available, including synthetic polyisoprene ("synthetic natural rubber").
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Many synthetic polymers remain in this state to well above room temperature.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.Polymers are studied in the fields of polymer chemistry, polymer physics, and polymer science.^ Physical chemistry of polymers and of soft condensed matter at the nanoscale .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Polymer Science and Engineering Publications in other areas of research may be found in the Departmental Home Pages of Chemistry and Chemical Engineering .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Studies of the Director Field in Shear Flow for Nematic solutions of a Rodlike Polymer", K. Matsuoka; G. C. Berry, Nihon Reorojii Dakkaishi 24, 75-85 (1996).
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

Contents

Etymology

.The word polymer is derived from the Greek words πολυ- - poly- meaning "many"; and μέρος - meros meaning "part". The term was coined in 1833 by Joens Jakob Berzelius, although his definition of a polymer was quite different from the modern definition.^ The terms polymer and monomer were derived from the Greek roots poly (many), mono (one) and meros (part).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Many common and useful polymers, such as polystyrene, polyacrylonitrile and poly(vinyl chloride) are atactic as normally prepared.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ The term alkyd derives from the two words alc ohol and ac id.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

(see New chemical terms)

Historical development

.Starting in 1811, Henri Braconnot did pioneering work in derivative cellulose compounds, perhaps the earliest important work in polymer science.^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Some important natural polymers Polymers derived from plants have been essential components of human existence for thousands of years.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.The development of vulcanization later in the nineteenth century improved the durability of the natural polymer rubber, signifying the first popularized semi-synthetic polymer.^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Natural rubber continues to have a large market despite the many forms of synthetic rubber available, including synthetic polyisoprene ("synthetic natural rubber").
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Raw natural rubber tends to be sticky when warm and brittle when cold, so it was little more than a novelty material when first introduced to Europe around 1770.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.In 1907, Leo Baekeland created the first completely synthetic polymer, Bakelite, by reacting phenol and formaldehyde at precisely controlled temperature and pressure.^ It was developed in 1907-1909 by the Belgian chemist Leo Baekeland , hence the common name bakelite .
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ As with all polymerizations, chains having a range of molecular weights are produced, and this range can be altered by controlling the pressure and temperature of the process.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ The initial display is of Bakelite, one of the first completely synthetic plastics to see commercial use (circa 1910).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

Bakelite was then publicly introduced in 1909.
.Despite significant advances in synthesis and characterization of polymers, a correct understanding of polymer molecular structure did not emerge until the 1920s.^ E-Mail: Interests: polymer blends; polymer composites; polymer membranes and membrane separations; gas permeability; polymer structure/property relationships; polymers for emerging technologies .
  • Editors - MDPI 23 January 2010 22:16 UTC www.mdpi.com [Source type: Academic]

^ ISI abstract ] P. Clemenson et al., "Synthesis and Characterization of New Water-Soluble Precursors of Polyimides", Polymer Engineering And Science, Jun.
  • Composite solid polymer electrolyte membranes (US6248469) 10 January 2010 19:43 UTC www.delphion.com [Source type: Academic]

^ Ueda et al., "Synthesis and Characterization of Aromatic PES Containing Pendant Sodium Sulfonate Groups", J. Polymer Science, vol.
  • Composite solid polymer electrolyte membranes (US6248469) 10 January 2010 19:43 UTC www.delphion.com [Source type: Academic]

.Before then, scientists believed that polymers were clusters of small molecules (called colloids), without definite molecular weights, held together by an unknown force, a concept known as association theory.^ Polymers are constructed from relatively small molecular fragments known as monomers that are joined together.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ "Crossover behavior in the viscosity of semiflexible polymers: Solutions of sodium hyaluronate as a function of concentration, molecular weight and temperature", M. Milas; I. Roure; G. C. Berry, J. Rheol.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ As the weight dispersion of molecules in a sample narrows, M w approaches M n , and in the unlikely case that all the polymer molecules have identical weights (a pure monodisperse sample), the ratio M w / M n becomes unity.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.In 1922, Hermann Staudinger proposed that polymers consisted of long chains of atoms held together by covalent bonds, an idea which did not gain wide acceptance for over a decade and for which Staudinger was ultimately awarded the Nobel Prize.^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Polymers formed by a straightforward linking together of monomer units, with no loss or gain of material, are called addition polymers or chain-growth polymers .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ The two open bonds remaining at the ends of the long chain of carbons (colored magenta) are normally not specified, because the atoms or groups found there depend on the chemical process used for polymerization.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Work by Wallace Carothers in the 1920s also demonstrated that polymers could be synthesized rationally from their constituent monomers.^ And see also this Wikipedia article on Wallace Carothers and his work on Neoprene, polyesters, and Nylon.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.An important contribution to synthetic polymer science was made by the Italian chemist Giulio Natta and the German chemist Karl Ziegler, who won the Nobel Prize in Chemistry in 1963 for the development of the Ziegler-Natta catalyst.^ For his contributions to chemistry, Staudinger received the 1953 Nobel Prize.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ The two shared the 1963 Nobel Prize in Chemistry .
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ For this important discovery these chemists received the 1963 Nobel Prize in chemistry .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Further recognition of the importance of polymers came with the award of the Nobel Prize in Chemistry in 1974 to Paul Flory, whose extensive work on polymers included the kinetics of step-growth polymerization and of addition polymerization, chain transfer, excluded volume, the Flory-Huggins solution theory, and the Flory convention.^ In theory, only a single chain-initiation process needs to take place, and the chain-propagation step then repeats itself indefinitely, but in practice multiple initiation steps are required, and eventually two radicals react ( chain termination ) to bring the polymerization to a halt.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Nevertheless, the polymer clearly forms by a step-growth process.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Chain transfer reactions are especially prevalent in the high pressure radical polymerization of ethylene, which is the method used to make LDPE (low density polyethylene).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Synthetic polymer materials such as nylon, polyethylene, Teflon, and silicone have formed the basis for a burgeoning polymer industry.^ The polyester Dacron and the polyamide Nylon 66, shown here, are two examples of synthetic condensation polymers, also known as step-growth polymers.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Polymers formed by a straightforward linking together of monomer units, with no loss or gain of material, are called addition polymers or chain-growth polymers .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.These years have also shown significant developments in rational polymer synthesis.^ Since that time, more recently developed polymers have largely displaced these uses.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.Most commercially important polymers today are entirely synthetic and produced in high volume on appropriately scaled organic synthetic techniques.^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ About 20% of the commercially-produced polymers are thermosets; the remainder are thermoplastics.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Silicones Polysiloxanes (–Si–O–Si-) are the most important of the small class inorganic polymers .
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

Synthetic polymers today find application in nearly every industry and area of life. .Polymers are widely used as adhesives and lubricants, as well as structural components for products ranging from children's toys to aircraft.^ Polysaccharides are polymers of sugars ; they play essential roles in energy storage, signalling, and as structural components in all living organisms.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ These polymers have an exceptionally wide range of uses — rope, binder covers, plastic bottles, staple yarns, non-woven fabrics, electric kettles.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ This clear, colorless polymer is widely used in place of glass, where its greater impact resistance, lighter weight, and machineability are advantages.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

They have been employed in a variety of biomedical applications ranging from implantable devices to controlled drug delivery. .Polymers such as poly(methyl methacrylate) find application as photoresist materials used in semiconductor manufacturing and low-k dielectrics for use in high-performance microprocessors.^ Chain transfer reactions are especially prevalent in the high pressure radical polymerization of ethylene, which is the method used to make LDPE (low density polyethylene).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ At low temperatures, chain transfer reactions are rare in such polymerizations, so the resulting polymers are cleanly linear (unbranched).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ ITW Plexus manufactures and sells the patented new Plexus methacrylate adhesives for structural bonding of nearly all thermoplastics, metals and composite materials.
  • ITW Polymers & Fluids 23 January 2010 22:16 UTC www.itw.com [Source type: Reference]

.Recently, polymers have also been employed as flexible substrates in the development of organic light-emitting diodes for electronic display.^ Fax: +82 544 787 710 Website: http://kit.kumoh.ac.kr/~dhhwang/ E-Mail: Interests: polymer synthesis; organic electronic materials; polymer light-emitting diodes; organic thin film transistors; organic photovoltaic devices; dye-sensitized solar cells, organic memory devices; photo-curable polymers; organic insulators; photo-resists .
  • Editors - MDPI 23 January 2010 22:16 UTC www.mdpi.com [Source type: Academic]

^ Since that time, more recently developed polymers have largely displaced these uses.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

Polymer synthesis

The repeating unit of the polymer polypropylene
.Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain.^ As with all polymerizations, chains having a range of molecular weights are produced, and this range can be altered by controlling the pressure and temperature of the process.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ This method (also known as step-growth ) requires that the monomers possess two or more kinds of functional groups that are able to react with each other in such a way that parts of these groups combine to form a small molecule (often H 2 O) which is eliminated from the two pieces.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ If the carbon chain contains double bonds, then cis-trans isomerism becomes possible, giving rise to two different possible configurations (known as diastereomers ) at each unit of the chain.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

During the polymerization process, some chemical groups may be lost from each monomer. This is the case, for example, in the polymerization of PET polyester. .The monomers are terephthalic acid (HOOC-C6H4-COOH) and ethylene glycol (HO-CH2-CH2-OH) but the repeating unit is -OC-C6H4-COO-CH2-CH2-O-, which corresponds to the combination of the two monomers with the loss of two water molecules.^ Polymers formed by a straightforward linking together of monomer units, with no loss or gain of material, are called addition polymers or chain-growth polymers .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ This method (also known as step-growth ) requires that the monomers possess two or more kinds of functional groups that are able to react with each other in such a way that parts of these groups combine to form a small molecule (often H 2 O) which is eliminated from the two pieces.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ The repeating structural unit of most simple polymers not only reflects the monomer(s) from which the polymers are constructed, but also provides a concise means for drawing structures to represent these macromolecules.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.The distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue.^ Polymers are constructed from relatively small molecular fragments known as monomers that are joined together.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Amylopectin is a much larger polymer having up to two million glucose residues arranged into branches of 20 to 30 units.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Synthetic polymers, which includes the large group known as plastics , came into prominence in the early twentieth century.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

Laboratory synthesis

.Laboratory synthetic methods are generally divided into two categories, step-growth polymerization and chain-growth polymerization[4].^ In theory, only a single chain-initiation process needs to take place, and the chain-propagation step then repeats itself indefinitely, but in practice multiple initiation steps are required, and eventually two radicals react ( chain termination ) to bring the polymerization to a halt.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Chain transfer reactions are especially prevalent in the high pressure radical polymerization of ethylene, which is the method used to make LDPE (low density polyethylene).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ The polyester Dacron and the polyamide Nylon 66, shown here, are two examples of synthetic condensation polymers, also known as step-growth polymers.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.The essential difference between the two is that in chain growth polymerization, monomers are added to the chain one at a time only[5], whereas in step-growth polymerization chains of monomers may combine with one another directly[6].^ In theory, only a single chain-initiation process needs to take place, and the chain-propagation step then repeats itself indefinitely, but in practice multiple initiation steps are required, and eventually two radicals react ( chain termination ) to bring the polymerization to a halt.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ If the two remaining groups are different (say one hydrogen and the other methyl), then the above conditions are satisfied and this part of the chain can give rise to two enantiomeric forms.
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^ This method (also known as step-growth ) requires that the monomers possess two or more kinds of functional groups that are able to react with each other in such a way that parts of these groups combine to form a small molecule (often H 2 O) which is eliminated from the two pieces.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

However, some newer methods such as plasma polymerization do not fit neatly into either category. .Synthetic polymerization reactions may be carried out with or without a catalyst.^ Further polymerization at the new radical site generates a side chain radical, and this may in turn lead to creation of other side chains by chain transfer reactions.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

Laboratory synthesis of biopolymers, especially of proteins, is an area of intensive research.

Biological synthesis

There are three main classes of biopolymers: polysaccharides, polypeptides, and polynucleotides. In living cells, they may be synthesized by enzyme-mediated processes, such as the formation of DNA catalyzed by DNA polymerase. .The synthesis of proteins involves multiple enzyme-mediated processes to transcribe genetic information from the DNA to RNA and subsequently translate that information to synthesize the specified protein from amino acids.^ Notice that the two copolymer sub-units are held together by peptide bonds, the same kinds that join amino acids into proteins.
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^ This occurs, for example, in the synthesis of the Nylon family of polymers in which the eliminated H 2 O molecule comes from the hydroxyl group of the acid and one of the amino hydrogens: .
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The protein may be modified further following translation in order to provide appropriate structure and functioning.

Modification of natural polymers

.Many commercially important polymers are synthesized by chemical modification of naturally occurring polymers.^ Name two kinds of commercially-important natural polymers.
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^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ Some important natural polymers Polymers derived from plants have been essential components of human existence for thousands of years.
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.Prominent examples include the reaction of nitric acid and cellulose to form nitrocellulose and the formation of vulcanized rubber by heating natural rubber in the presence of sulfur.^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

^ A comparison of the properties of polyethylene (both LDPE & HDPE) with the natural polymers rubber and cellulose is instructive.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Natural rubber continues to have a large market despite the many forms of synthetic rubber available, including synthetic polyisoprene ("synthetic natural rubber").
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Polymer properties

.Polymer properties are broadly divided into several classes based on the scale at which the property is defined as well as upon its physical basis[7].^ Physical properties of polymers .
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^ In practice, it is usually sufficient to classify chiral polymers into the following three classes of stereoregularity , usually referred to as tact icity.
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^ The physical properties of a polymer such as its strength and flexibility depend on: .
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.The most basic property of a polymer is the identity of its constituent monomers.^ The repeating structural unit of most simple polymers not only reflects the monomer(s) from which the polymers are constructed, but also provides a concise means for drawing structures to represent these macromolecules.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.A second set of properties, known as microstructure, essentially describe the arrangement of these monomers within the polymer at the scale of a single chain.^ These properties have their origins in the nature of the monomers used to produce them.
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^ In plants, these glucose-polymer reserves are known as starch .
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^ In a linear polymer such as polyethylene, rotations around carbon-carbon single bonds can allow the chains to bend or curl up in various ways, resulting in the spaghetti-like mixture of these different conformations we alluded to above.
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.These basic structural properties play a major role in determining bulk physical properties of the polymer, which describe how the polymer behaves as a continuous macroscopic material.^ Physical properties of polymers .
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^ Polysaccharides are polymers of sugars ; they play essential roles in energy storage, signalling, and as structural components in all living organisms.
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^ The repeating structural unit of most simple polymers not only reflects the monomer(s) from which the polymers are constructed, but also provides a concise means for drawing structures to represent these macromolecules.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Chemical properties, at the nano-scale, describe how the chains interact through various physical forces.^ Polymers can be classified according to their chemical composition, their physical properties, and their general application.
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.At the macro-scale, they describe how the bulk polymer interacts with other chemicals and solvents.^ They accomplish this by taking up space between the polymer chains and acting as lubricants to enable the chains to more readily slip over each other.
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^ The synthetic methods used to prepare this and other polymers will be described later in this chapter.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

Monomers and repeat units

.The identity of the monomer residues (repeat units) comprising a polymer is its first and most important attribute.^ Silicones Polysiloxanes (–Si–O–Si-) are the most important of the small class inorganic polymers .
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^ Polymers formed by a straightforward linking together of monomer units, with no loss or gain of material, are called addition polymers or chain-growth polymers .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ The repeating structural unit of most simple polymers not only reflects the monomer(s) from which the polymers are constructed, but also provides a concise means for drawing structures to represent these macromolecules.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Polymer nomenclature is generally based upon the type of monomer residues comprising the polymer.^ There are two general types of hazards that polymers can introduce into the aquatic environment.
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.Polymers that contain only a single type of repeat unit are known as homopolymers, while polymers containing a mixture of repeat units are known as copolymers.^ A polymer that is composed of identical monomeric units (as is polyethylene) is called a homopolymer .
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^ Most direct copolymerizations of equimolar mixtures of different monomers give statistical copolymers, or if one monomer is much more reactive a nearly homopolymer of that monomer.
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^ If the carbon chain contains double bonds, then cis-trans isomerism becomes possible, giving rise to two different possible configurations (known as diastereomers ) at each unit of the chain.
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Poly(styrene), for example, is composed only of styrene monomer residues, and is therefore classified as a homopolymer. .Ethylene-vinyl acetate, on the other hand, contains more than one variety of repeat unit and is thus a copolymer.^ Most direct copolymerizations of equimolar mixtures of different monomers give statistical copolymers, or if one monomer is much more reactive a nearly homopolymer of that monomer.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Heteropolymers are built up from more than one type of monomer.
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^ The synthesis of macromolecules composed of more than one monomeric repeating unit has been explored as a means of controlling the properties of the resulting material.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Some biological polymers are composed of a variety of different but structurally related monomer residues; for example, polynucleotides such as DNA are composed of a variety of nucleotide subunits.^ An excellent and concise Polymer History article by Dorel Feldman appeared in Designed Monomers & Polymers 11(1) 2008, and is available online in some academic libraries.
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^ The repeating structural unit of most simple polymers not only reflects the monomer(s) from which the polymers are constructed, but also provides a concise means for drawing structures to represent these macromolecules.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ But if one of the hydrogen atoms is replaced by some other entity such as a methyl group, the relative orientations of the individual monomer units that make up a linear section of any carbon chain becomes an important characteristic of the polymer.
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A polymer molecule containing ionizable subunits is known as a polyelectrolyte or ionomer.

Microstructure

.The microstructure of a polymer (sometimes called configuration) relates to the physical arrangement of monomer residues along the backbone of the chain[8].^ It is sometimes interpreted as the temperature above which significant portions of polymer chains are able to slide past each other in response to an applied force.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ If all the substituents lie on one side of the chain the configuration is called isotactic .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Polymers formed by a straightforward linking together of monomer units, with no loss or gain of material, are called addition polymers or chain-growth polymers .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.These are the elements of polymer structure that require the breaking of a covalent bond in order to change.^ The repeating structural unit of most simple polymers not only reflects the monomer(s) from which the polymers are constructed, but also provides a concise means for drawing structures to represent these macromolecules.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Structure has a strong influence on the other properties of a polymer.^ The tacticity of a polymer chain can have a major influence on its properties.
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.For example, two samples of natural rubber may exhibit different durability, even though their molecules comprise the same monomers.^ For example, the latex in natural rubber is made mostly of cis -polyisoprene, whereas the trans isomer (known as gutta percha latex) has very different (and generally inferior) properties.
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^ The HDPE molecules, for example, are all long carbon chains, but the lengths may vary by thousands of monomer units.
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^ In the following example, the same bisphenol A intermediate used as a monomer for Lexan serves as a difunctional scaffold to which the epoxide rings are attached.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

Polymer architecture

Branch point in a polymer
An important microstructural feature determining polymer properties is the polymer architecture.[9] .The simplest polymer architecture is a linear chain: a single backbone with no branches.^ Nonlinear behavior of branched and linear flexible chain polymers .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ A general diagram illustrating this assembly of linear macromolecules, which supports the name chain growth polymers , is presented here.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ In a linear polymer such as polyethylene, rotations around carbon-carbon single bonds can allow the chains to bend or curl up in various ways, resulting in the spaghetti-like mixture of these different conformations we alluded to above.
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A related unbranching architecture is a ring polymer. .A branched polymer molecule is composed of a main chain with one or more substituent side chains or branches.^ If all the substituents lie on one side of the chain the configuration is called isotactic .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Unlike simpler pure compounds, most polymers are not composed of identical molecules.
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^ In contrast, LDPE is composed of smaller and more highly branched chains which do not easily adopt crystalline structures.
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Special types of branched polymers include star polymers, comb polymers, brush polymers, dendronized polymers, ladders, and dendrimers[9].
.Branching of polymer chains affects the ability of chains to slide past one another by altering intermolecular forces, in turn affecting bulk physical polymer properties.^ Physical properties of polymers .
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^ It is sometimes interpreted as the temperature above which significant portions of polymer chains are able to slide past each other in response to an applied force.
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^ As the name implies, this reaction moves a carbon radical from one location to another by an intermolecular or intramolecular hydrogen atom transfer (colored green).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Long chain branches may increase polymer strength, toughness, and the glass transition temperature due to an increase in the number of entanglements per chain.^ This defines the glass transition temperature t g .
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^ At low temperatures, the tangled polymer chains tend to behave as rigid glasses.
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^ The HDPE molecules, for example, are all long carbon chains, but the lengths may vary by thousands of monomer units.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.The effect of such long-chain branches on the size of the polymer in solution is characterized by the branching index.^ At low temperatures, chain transfer reactions are rare in such polymerizations, so the resulting polymers are cleanly linear (unbranched).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ If the cross-links are fairly long and flexible, adjacent chains can move with respect to each other, producing an elastic polymer or elastomer .
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^ Don't be misled by chemical formulas that depict polymers such as polyethylene as reasonably straight chains of substituted carbon atoms.
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.Random length and atactic short chains, on the other hand, may reduce polymer strength due to disruption of organization and may likewise reduce the crystallinity of the polymer.^ They accomplish this by taking up space between the polymer chains and acting as lubricants to enable the chains to more readily slip over each other.
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^ If the cross-links are fairly long and flexible, adjacent chains can move with respect to each other, producing an elastic polymer or elastomer .
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^ Polymers may also be classified as straight-chained or branched, leading to forms such as these: .
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A good example of this effect is related to the range of physical attributes of polyethylene. .High-density polyethylene (HDPE) has a very low degree of branching, is quite stiff, and is used in applications such as milk jugs.^ Polyethylene high density (HDPE) .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Polyethylene low density (LDPE) .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Chain transfer reactions are especially prevalent in the high pressure radical polymerization of ethylene, which is the method used to make LDPE (low density polyethylene).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

.Low-density polyethylene (LDPE), on the other hand, has significant numbers of both long and short branches, is quite flexible, and is used in applications such as plastic films.^ Polyethylene low density (LDPE) .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ A "very low density" form (VLDPE) with extensive short-chain branching is now used for plastic stretch wrap (replacing the original component of Saran Wrap) and in flexible tubing.
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^ Chain transfer reactions are especially prevalent in the high pressure radical polymerization of ethylene, which is the method used to make LDPE (low density polyethylene).
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

Dendrimer and dendron
.Dendrimers are a special case of polymer where every monomer unit is branched.^ Amylopectin is a much larger polymer having up to two million glucose residues arranged into branches of 20 to 30 units.
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^ This is especially the case with synthetic polymers, whose molecular weights cover a range of values, as may the sequence, orientation, and connectivity of the individual monomers.
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This tends to reduce intermolecular chain entanglement and crystallization. Alternatively, dendritic polymers are not perfectly branched but share similar properties to dendrimers due to their high degree of branching.
.The architecture of the polymer is often physically determined by the functionality of the monomers from which it is formed[10].^ This method (also known as step-growth ) requires that the monomers possess two or more kinds of functional groups that are able to react with each other in such a way that parts of these groups combine to form a small molecule (often H 2 O) which is eliminated from the two pieces.
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.This property of a monomer is defined as the number of reaction sites at which may form chemical covalent bonds.^ It employs a free-radical initiator that donates its unpaired electron to the monomer, making the latter highly reactive and able to form a bond with another monomer at this site.
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.The basic functionality required for forming even a linear chain is two bonding sites.^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
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^ If the two remaining groups are different (say one hydrogen and the other methyl), then the above conditions are satisfied and this part of the chain can give rise to two enantiomeric forms.
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^ This method (also known as step-growth ) requires that the monomers possess two or more kinds of functional groups that are able to react with each other in such a way that parts of these groups combine to form a small molecule (often H 2 O) which is eliminated from the two pieces.
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.Higher functionality yields branched or even crosslinked or networked polymer chains.^ Polymers may also be classified as straight-chained or branched, leading to forms such as these: .
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^ Nonlinear behavior of branched and linear flexible chain polymers .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ As might be expected, shorter and less-branched polymer chains can more easily organize themselves into ordered layers than can long chains.
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.An effect related to branching is chemical crosslinking - the formation of covalent bonds between chains.^ Hydrogen-bonding between adjacent chains also helps, and is very important in fiber-forming polymers both synthetic (Nylon 6.6) and natural (cotton cellulose).
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^ The high tensile strength is due in part to the extensive hydrogen bonding between adjacent chains.
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^ Extensive hydrogen bonding between the chains causes native celluose to be abut 70% crystalline.
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Crosslinking tends to increase Tg and increase strength and toughness. .Among other applications, this process is used to strengthen rubbers in a process known as vulcanization, which is based on crosslinking by sulfur.^ It did not become generally useful until the mid-nineteenth century when Charles Goodyear found that heating it with sulfur — a process he called vulcanization — could greatly improve its properties.
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^ Nitrocellulose was also used as an explosive and propellent, for which applications it is known as guncotton .
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^ PVA is too soft and low-melting to be used by itself; it is commonly employed as a water-based emulsion in paints, wood glue and other adhesives.
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Car tires, for example, are highly crosslinked in order to reduce the leaking of air out of the tire and to toughen their durability. Eraser rubber, on the other hand, is not crosslinked to allow flaking of the rubber and prevent damage to the paper.
.A cross-link suggests a branch point from which four or more distinct chains emanate.^ The thermoplastic materials described above are chains based on relatively simple monomeric units having varying degrees of polymerization, branching, bending, cross-linking and crystallinity, but with each molecular chain being a discrete unit.
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^ Control of polymerization by means of catalysts and additives has led to a large variety of materials based on polyethylene that exhibit differences in densities, degrees of chain branching and crystallinity, and cross-linking.
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^ If the cross-links are fairly long and flexible, adjacent chains can move with respect to each other, producing an elastic polymer or elastomer .
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A polymer molecule with a high degree of crosslinking is referred to as a polymer network.[11] .Sufficiently high crosslink concentrations may lead to the formation of an infinite network, also known as a gel, in which networks of chains are of unlimited extent—essentially all chains have linked into one molecule.^ In order to make this happen, a chemically active molecule (called an initiator ) is needed to start what is known as a chain reaction .
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^ Polymers may also be classified as straight-chained or branched, leading to forms such as these: .
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^ How polymers are made Polymers are made by joining small molecules into large ones.
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[12]

Chain length

.The physical properties of a polymer are strongly dependent on the size or length of the polymer chain.^ Physical properties of polymers .
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^ The physical properties of a polymer such as its strength and flexibility depend on: .
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^ It is also the simplest polymer, consisting of random-length (but generally very long) chains made up of two-carbon units.
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[13]. For example, as chain length is increased, melting and boiling temperatures increase quickly[13]. .Impact resistance also tends to increase with chain length, as does the viscosity, or resistance to flow, of the polymer in its melt state[14].^ At low temperatures, the tangled polymer chains tend to behave as rigid glasses.
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^ This clear, colorless polymer is widely used in place of glass, where its greater impact resistance, lighter weight, and machineability are advantages.
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^ It is also the simplest polymer, consisting of random-length (but generally very long) chains made up of two-carbon units.
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.Chain length is related to melt viscosity roughly as 1:103.2, so that a tenfold increase in polymer chain length results in a viscosity increase of over 1000 times[citation needed].^ It is also the simplest polymer, consisting of random-length (but generally very long) chains made up of two-carbon units.
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.Increasing chain length furthermore tends to decrease chain mobility, increase strength and toughness, and increase the glass transition temperature (Tg)[citation needed].^ This defines the glass transition temperature t g .
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^ At low temperatures, the tangled polymer chains tend to behave as rigid glasses.
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^ These substances are compounded into certain types of plastics to render them more flexible by lowering the glass transition temperature.
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.This is a result of the increase in chain interactions such as Van der Waals attractions and entanglements that come with increased chain length[citation needed].^ Retarded van der Waals attraction .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Direct Measurement of Retarded van der Waals Attraction", M.A. Bevan and D.C. Prieve, Langmuir (submitted).
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

.These interactions tend to fix the individual chains more strongly in position and resist deformations and matrix breakup, both at higher stresses and higher temperatures[citation needed].^ Many of these factors are strongly interdependent, and most are discussed in much more detail in subsequent sections of this page.
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^ At low temperatures, the tangled polymer chains tend to behave as rigid glasses.
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.A common means of expressing the length of a chain is the degree of polymerization, which quantifies the number of monomers incorporated into the chain[15][16].^ Addition or chain-growth polymerization involves the rearrangement of bonds within the monomer in such a way that the monomers link up directly with each other: .
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^ Control of polymerization by means of catalysts and additives has led to a large variety of materials based on polyethylene that exhibit differences in densities, degrees of chain branching and crystallinity, and cross-linking.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.As with other molecules, a polymer's size may also be expressed in terms of molecular weight.^ "Crossover behavior in the viscosity of semiflexible polymers: Solutions of sodium hyaluronate as a function of concentration, molecular weight and temperature", M. Milas; I. Roure; G. C. Berry, J. Rheol.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Well-defined oligomers and high molecular weight polymers .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ This is especially the case with synthetic polymers, whose molecular weights cover a range of values, as may the sequence, orientation, and connectivity of the individual monomers.
  • Polymers and plastics: a chemical introduction 23 January 2010 22:16 UTC www.chem1.com [Source type: FILTERED WITH BAYES]

.Since synthetic polymerization techniques typically yield a polymer product including a range of molecular weights, the weight is often expressed statistically to describe the distribution of chain lengths present in the same.^ "Crossover behavior in the viscosity of semiflexible polymers: Solutions of sodium hyaluronate as a function of concentration, molecular weight and temperature", M. Milas; I. Roure; G. C. Berry, J. Rheol.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Well-defined oligomers and high molecular weight polymers .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Crossover behavior in the viscosity of semiflexible polymers: Intermolecular interactions as a function of concentration and molecular weight", G. C. Berry, J. Rheol.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

Common examples are the number average molecular weight and weight average molecular weight[17][18]. The ratio of these two values is the polydispersity index, commonly used to express the "width" of the molecular weight distribution.[19] A final measurement is contour length, which can be understood as the length of the chain backbone in its fully extended state[20].
.The flexibility of an unbranched chain polymer is characterized by its persistence length.^ Intermolecular interactions in "entangled" solutions of flexible chain polymers .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Rheology of blends of liquid crystalline and flexible chain polymers", G. C. Berry, Trends Poly.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Nonlinear behavior of branched and linear flexible chain polymers .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

Monomer arrangement in copolymers

Different types of copolymers
Monomers within a copolymer may be organized along the backbone in a variety of ways.
  • Alternating copolymers possess regularly alternating monomer residues:[21] [AB...]n (2).
  • Periodic copolymers have monomer residue types arranged in a repeating sequence: [AnBm...] m being different from n .
  • Statistical copolymers have monomer residues arranged according to a known statistical rule. A statistical copolymer in which the probability of finding a particular type of monomer residue at an particular point in the chain is independent of the types of surrounding monomer residue may be referred to as a truly random copolymer[22][23] (3).
  • Block copolymers have two or more homopolymer subunits linked by covalent bonds[21] (4). Polymers with two or three blocks of two distinct chemical species (e.g., A and B) are called diblock copolymers and triblock copolymers, respectively. .Polymers with three blocks, each of a different chemical species (e.g., A, B, and C) are termed triblock terpolymers.
  • Graft or grafted copolymers contain side chains that have a different composition or configuration than the main chain.^ Block, graft and gradient copolymers .
    • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

    (5)

Tacticity

Tacticity describes the relative stereochemistry of chiral centers in neighboring structural units within a macromolecule. There are three types: isotactic (all substituents on the same side), atactic (random placement of substituents), and syndiotactic (alternating placement of substituents).

Polymer morphology

Polymer morphology generally describes the arrangement of chains in space and microscopic ordering of many polymer chains.

Crystallinity

When applied to polymers, the term crystalline has a somewhat ambiguous usage. In some cases, the term crystalline finds identical usage to that used in conventional crystallography. For example, the structure of a crystalline protein or polynucleotide, such as a sample prepared for x-ray crystallography, may be defined in terms of a conventional unit cell composed of one or more polymer molecules with cell dimensions of hundreds of angstroms or more.
A synthetic polymer may be lightly described as crystalline if it contains regions of three-dimensional ordering on atomic (rather than macromolecular) length scales, usually arising from intramolecular folding and/or stacking of adjacent chains. Synthetic polymers may consist of both crystalline and amorphous regions; the degree of crystallinity may be expressed in terms of a weight fraction or volume fraction of crystalline material. Few synthetic polymers are entirely crystalline.[24]
The crystallinity of polymers is characterized by their degree of crystallinity, ranging from zero for a completely non-crystalline polymer to one for a theoretical completely crystalline polymer. Polymers with microcrystalline regions are generally tougher (can be bent more without breaking) and more impact-resistant than totally amorphous polymers.[25]
Polymers with a degree of crystallinity approaching zero or one will tend to be transparent, while polymers with intermediate degrees of crystallinity will tend to be opaque due to light scattering by crystalline or glassy regions. Thus for many polymers, reduced crystallinity may also be associated with increased transparency.

Chain conformation

The space occupied by a polymer molecule is generally expressed in terms of radius of gyration, which is an average distance from the center of mass of the chain to the chain itself. Alternatively, it may be expressed in terms of pervaded volume, which is the volume of solution spanned by the polymer chain and scales with the cube of the radius of gyration.[26]

Mechanical properties

The bulk properties of a polymer are those most often of end-use interest. .These are the properties that dictate how the polymer actually behaves on a macroscopic scale.^ These Earrings with Roses appear to be Antique, but are actually hand sculpted from Polymer Clay.  They dangle from the Rose Post.
  • Polymer Clay Jewelry 10 January 2010 19:43 UTC site.netopia.com [Source type: General]

Tensile strength

The tensile strength of a material quantifies how much stress the material will endure before suffering permanent deformation.[27][28] This is very important in applications that rely upon a polymer's physical strength or durability. For example, a rubber band with a higher tensile strength will hold a greater weight before snapping. In general, tensile strength increases with polymer chain length and crosslinking of polymer chains.

Young's modulus of elasticity

Young's Modulus quantifies the elasticity of the polymer. It is defined, for small strains, as the ratio of rate of change of stress to strain. Like tensile strength, this is highly relevant in polymer applications involving the physical properties of polymers, such as rubber bands. The modulus is strongly dependent on temperature.

Transport properties

Transport properties such as diffusivity relate to how rapidly molecules move through the polymer matrix. These are very important in many applications of polymers for films and membranes.

Phase behavior

Melting point

.The term melting point, when applied to polymers, suggests not a solid-liquid phase transition but a transition from a crystalline or semi-crystalline phase to a solid amorphous phase.^ "Rheology of blends of liquid crystalline and flexible chain polymers", G. C. Berry, Trends Poly.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Orthogonal and Parallel Superposition Measurements on Lyotropic Liquid Crystalline Polymers" L. M. Walker; J. Vermant; P. Moldenaers; J. Mewis, Rheologica Acta 39:26-37 (2000) .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

Though abbreviated as simply Tm, the property in question is more properly called the crystalline melting temperature. Among synthetic polymers, crystalline melting is only discussed with regards to thermoplastics, as thermosetting polymers will decompose at high temperatures rather than melt.

Boiling point

The boiling point of a polymeric material is strongly dependent on chain length. High polymers with a large degree of polymerization do not exhibit a boiling point because they decompose before reaching theoretical boiling temperatures. For shorter oligomers, a boiling transition may be observed and will generally increase rapidly as chain length is increased.

Glass transition temperature

.A parameter of particular interest in synthetic polymer manufacturing is the glass transition temperature (Tg), which describes the temperature at which amorphous polymers undergo a second-order phase transition from a rubbery, viscous amorphous solid, or from a crystalline solid (depending on the degree of crystallization) to a brittle, glassy amorphous solid.^ "Photon correlation spectroscopy of bulk poly(n-hexyl methacrylate) near the glass transition", Y. Hwang; G. D. Patterson; J. R. Stevens, J. Polym.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

.The glass transition temperature may be engineered by altering the degree of branching or crosslinking in the polymer or by the addition of plasticizer.^ Polymer Science and Engineering Publications in other areas of research may be found in the Departmental Home Pages of Chemistry and Chemical Engineering .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Photon correlation spectroscopy of bulk poly(n-hexyl methacrylate) near the glass transition", Y. Hwang; G. D. Patterson; J. R. Stevens, J. Polym.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

[29]

Mixing behavior

Phase diagram of the typical mixing behavior of weakly interacting polymer solutions.
In general, polymeric mixtures are far less miscible than mixtures of small molecule materials. This effect results from the fact that the driving force for mixing is usually entropy, not interaction energy. In other words, miscible materials usually form a solution not because their interaction with each other is more favorable than their self-interaction, but because of an increase in entropy and hence free energy associated with increasing the amount of volume available to each component. This increase in entropy scales with the number of particles (or moles) being mixed. Since polymeric molecules are much larger and hence generally have much higher specific volumes than small molecules, the number of molecules involved in a polymeric mixture is far smaller than the number in a small molecule mixture of equal volume. The energetics of mixing, on the other hand, is comparable on a per volume basis for polymeric and small molecule mixtures. This tends to increase the free energy of mixing for polymer solutions and thus make solvation less favorable. .Thus, concentrated solutions of polymers are far rarer than those of small molecules.^ "Crossover behavior in the viscosity of semiflexible polymers: Solutions of sodium hyaluronate as a function of concentration, molecular weight and temperature", M. Milas; I. Roure; G. C. Berry, J. Rheol.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Characterization of polymers in moderately concentrated solutions via static and dynamic light scattering .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Rheological properties of moderately concentrated solutions nematic polymers .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

.Furthermore, the phase behavior of polymer solutions and mixtures is more complex than that of small molecule mixtures.^ "Crossover behavior in the viscosity of semiflexible polymers: Solutions of sodium hyaluronate as a function of concentration, molecular weight and temperature", M. Milas; I. Roure; G. C. Berry, J. Rheol.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

.Whereas most small molecule solutions exhibit only an upper critical solution temperature phase transition, at which phase separation occurs with cooling, polymer mixtures commonly exhibit a lower critical solution temperature phase transition, at which phase separation occurs with heating.^ "Crossover behavior in the viscosity of semiflexible polymers: Solutions of sodium hyaluronate as a function of concentration, molecular weight and temperature", M. Milas; I. Roure; G. C. Berry, J. Rheol.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

.In dilute solution, the properties of the polymer are characterized by the interaction between the solvent and the polymer.^ Characterization of polymers in moderately concentrated solutions via static and dynamic light scattering .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Rheological properties of moderately concentrated solutions nematic polymers .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Intermolecular interactions in "entangled" solutions of flexible chain polymers .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

In a good solvent, the polymer appears swollen and occupies a large volume. .In this scenario, intermolecular forces between the solvent and monomer subunits dominate over intramolecular interactions.^ "The Interaction between Adsorbed Layers of Lysozyme Studied with the Surface Force Technique", E. Blomberg, P.M. Claesson, J.C. Froberg and R.D. Tilton, Langmuir 10, 2325 (1994).
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

In a bad solvent or poor solvent, intramolecular forces dominate and the chain contracts. In the theta solvent, or the state of the polymer solution where the value of the second virial coefficient becomes 0, the intermolecular polymer-solvent repulsion balances exactly the intramolecular monomer-monomer attraction. Under the theta condition (also called the Flory condition), the polymer behaves like an ideal random coil.

Inclusion of plasticizers

Inclusion of plasticizers tends to lower Tg and increase polymer flexibility. Plasticizers are generally small molecules that are chemically similar to the polymer and create gaps between polymer chains for greater mobility and reduced interchain interactions. A good example of the action of plasticizers is related to polyvinylchlorides or PVCs. A uPVC, or unplasticized polyvinylchloride, is used for things such as pipes. A pipe has no plasticizers in it, because it needs to remain strong and heat-resistant. Plasticized PVC is used for clothing for a flexible quality. Plasticizers are also put in some types of cling film to make the polymer more flexible.

Chemical properties

.The attractive forces between polymer chains play a large part in determining a polymer's properties.^ Polymer: A polymer is a large molecule with high molecular weight formed by similar monomers or simple molecules linked together in a chain-like fashion.
  • U.S. Emulsion Polymers Markets 23 January 2010 22:16 UTC www.frost.com [Source type: Reference]

^ It is sometimes interpreted as the temperature above which significant portions of polymer chains are able to slide past each other in response to an applied force.
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Synthetic polymers are produced commercially on a very large scale and have a wide range of properties and uses.
  • Chemical of the Week -- Polymers 10 January 2010 19:43 UTC scifun.chem.wisc.edu [Source type: Reference]

.Because polymer chains are so long, these interchain forces are amplified far beyond the attractions between conventional molecules.^ Polymer: A polymer is a large molecule with high molecular weight formed by similar monomers or simple molecules linked together in a chain-like fashion.
  • U.S. Emulsion Polymers Markets 23 January 2010 22:16 UTC www.frost.com [Source type: Reference]

^ This type of Polymer got its name because it is a polymer having functional groups linked together by carbonate groups in its molecular chain.

^ Because every part of the ethylene monomer is included in the finished polymer, the free radical polymerization of polyethylene is referred to as an addition polymerization; the ethylene molecules are simply added together.
  • How are polymers made?: Scientific American 10 January 2010 19:43 UTC www.scientificamerican.com [Source type: FILTERED WITH BAYES]

Different side groups on the polymer can lend the polymer to ionic bonding or hydrogen bonding between its own chains. These stronger forces typically result in higher tensile strength and higher crystalline melting points.
The intermolecular forces in polymers can be affected by dipoles in the monomer units. Polymers containing amide or carbonyl groups can form hydrogen bonds between adjacent chains; the partially positively charged hydrogen atoms in N-H groups of one chain are strongly attracted to the partially negatively charged oxygen atoms in C=O groups on another. These strong hydrogen bonds, for example, result in the high tensile strength and melting point of polymers containing urethane or urea linkages. Polyesters have dipole-dipole bonding between the oxygen atoms in C=O groups and the hydrogen atoms in H-C groups. Dipole bonding is not as strong as hydrogen bonding, so a polyester's melting point and strength are lower than Kevlar's (Twaron), but polyesters have greater flexibility.
Ethene, however, has no permanent dipole. .The attractive forces between polyethylene chains arise from weak van der Waals forces.^ Retarded van der Waals attraction .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Direct Measurement of Retarded van der Waals Attraction", M.A. Bevan and D.C. Prieve, Langmuir (submitted).
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

Molecules can be thought of as being surrounded by a cloud of negative electrons. .As two polymer chains approach, their electron clouds repel one another.^ Polymers such as polyethylene, polystyrene, acrylic, and polyvinyl chloride are made by addition or chain-reaction polymerization where only one monomer species is used.

^ For example, instead of stealing an electron from double-bonded carbons or a nearby propagating chain, the carbon atom with the free radical sometimes steals an entire hydrogen atom from another chain end.
  • How are polymers made?: Scientific American 10 January 2010 19:43 UTC www.scientificamerican.com [Source type: FILTERED WITH BAYES]

^ The monomer ethylene is composed of two carbon atoms, each bonded to two hydrogen atoms and sharing a double bond with one another.
  • How are polymers made?: Scientific American 10 January 2010 19:43 UTC www.scientificamerican.com [Source type: FILTERED WITH BAYES]

.This has the effect of lowering the electron density on one side of a polymer chain, creating a slight positive dipole on this side.^ A polymer brush consists of end-tethered (grafted, anchored) polymer chains stretched away from the substrate due to the volume-excluded effect.

^ If all the substituents lie on one side of the chain the configuration is called isotactic .
  • Polymers 10 January 2010 19:43 UTC www.cem.msu.edu [Source type: Reference]

^ Many art supplies can be added to polymer clay to create some very beautiful effects.
  • Frequently Asked Questions about Polymer Clay 10 January 2010 19:43 UTC polyclay.com [Source type: FILTERED WITH BAYES]

This charge is enough to attract the second polymer chain. .Van der Waals forces are quite weak, however, so polyethylene can have a lower melting temperature compared to other polymers.^ Retarded van der Waals attraction .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Direct Measurement of Retarded van der Waals Attraction", M.A. Bevan and D.C. Prieve, Langmuir (submitted).
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

Standardized polymer nomenclature

There are multiple conventions for naming polymer substances. Many commonly used polymers, such as those found in consumer products, are referred to by a common or trivial name. The trivial name is assigned based on historical precedent or popular usage rather than a standardized naming convention. Both the American Chemical Society[30] and IUPAC[31] have proposed standardized naming conventions; the ACS and IUPAC conventions are similar but not identical.[32] Examples of the differences between the various naming conventions are given in the table below:
Common name ACS name IUPAC name
Poly(ethylene oxide) or PEO Poly(oxyethylene) Poly(oxyethene)
Poly(ethylene terephthalate) or PET Poly(oxy-1,2-ethanediyloxycarbonyl-1,4-phenylenecarbonyl) Poly(oxyetheneoxyterephthaloyl)
Nylon 6 Poly[amino(1-oxo-1,6-hexanediyl)] Poly[amino(1-oxohexan-1,6-diyl)]
In both standardized conventions, the polymers' names are intended to reflect the monomer(s) from which they are synthesized rather than the precise nature of the repeating subunit. For example, the polymer synthesized from the simple alkene ethene is called polyethylene, retaining the -ene suffix even though the double bond is removed during the polymerization process:
Ethene polymerization.png
Polyethene monomer.png

Polymer characterization

.The characterization of a polymer requires several parameters which need to be specified.^ The Polymers 2009 conference assembles an international community for the presentation of recent advances in polymer synthesis, physical characterization, and performance in several complementary emerging technologies.
  • Gordon Research Conferences - 2009 Program (Polymers) 23 January 2010 22:16 UTC grc.org [Source type: Academic]

This is because a polymer actually consists of a statistical distribution of chains of varying lengths, and each chain consists of monomer residues which affect its properties.
.A variety of lab techniques are used to determine the properties of polymers.^ Some (but not all) polymer clay techniques may be used for air-dry clay, but the main difference is that air-dry clay shall be allowed to dry, and it shall not be baked.

^ Synthetic polymers are produced commercially on a very large scale and have a wide range of properties and uses.
  • Chemical of the Week -- Polymers 10 January 2010 19:43 UTC scifun.chem.wisc.edu [Source type: Reference]

^ Polymers have many inherent properties that can be further enhanced by a wide range of additives to broaden their uses and applications.
  • Plastics Division : the basics - polymer definition and properties 10 January 2010 19:43 UTC www.americanchemistry.com [Source type: FILTERED WITH BAYES]

.Techniques such as wide angle X-ray scattering, small angle X-ray scattering, and small angle neutron scattering are used to determine the crystalline structure of polymers.^ Small angle light scattering studies of morphology in complex flow geometries .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Small angle Rayleigh light scattering by dispersions of relatively large particles", R.Y. Ofoli and D.C. Prieve, Langmuir 13, 4837 (1997).
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Kinetics of agglomeration as measured by small-angle light scattering .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

Gel permeation chromatography is used to determine the number average molecular weight, weight average molecular weight, and polydispersity. FTIR, Raman and NMR can be used to determine composition. .Thermal properties such as the glass transition temperature and melting point can be determined by differential scanning calorimetry and dynamic mechanical analysis.^ "Dynamic heterogeneity near the glass transition", G. D. Patterson; J. R. Stevens, J. Non-Cryst.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

Pyrolysis followed by analysis of the fragments is one more technique for determining the possible structure of the polymer. Thermogravimetry is a useful technique to evaluate the thermal stability of the polymer. Detailed analyses of TG curves also allow us to know a bit of the phase segregation in polymers. Rheological properties are also commonly used to help determine molecular architecture (molecular weight, molecular weight distribution and branching)as well as to understand how the polymer will process, through measurements of the polymer in the melt phase. .Another Polymer characterization technique is Automatic Continuous Online Monitoring of Polymerization Reactions (ACOMP) which provides real-time characterization of polymerization reactions.^ "Polymer rheology: Principles, Techniques and Applications" G. C. Berry, In Desk Reference of Polymer Characterization and Analysis; J. R. F. Brady, ed.; American Chemical Society: New York, 2000.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

It can be used as an analytical method in R&D, as a tool for reaction optimization at the bench and pilot plant level and, eventually, for feedback control of full-scale reactors. ACOMP measures in a model-independent fashion the evolution of average molar mass and intrinsic viscosity, monomer conversion kinetics and, in the case of copolymers, also the average composition drift and distribution. .It is applicable in the areas of free radical and controlled radical homo- and copolymerization, polyelectrolyte synthesis, heterogeneous phase reactions, including emulsion polymerization, adaptation to batch and continuous reactors, and modifications of polymers.^ "Controlled Radical Polymerization of Styrene with Nitronyl Nitroxides", T. Shigemoto, K. Matyjaszewski, Macromol.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ Controlled Radical Polymerization.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

^ "Controlled Radical Polymerization by Degenerative Transfer.
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

[33][34][35]

Polymer degradation

A plastic item with thirty years of exposure to heat and cold, brake fluid, and sunlight. Notice the discoloration, swollen dimensions, and tiny splits running through the material
Polymer degradation is a change in the properties—tensile strength, color, shape, molecular weight, etc.—of a polymer or polymer-based product under the influence of one or more environmental factors, such as heat, light, chemicals and, in some cases, galvanic action. It is often due to the hydrolysis of the bonds connecting the polymer chain, which in turn leads to a decrease in the molecular mass of the polymer. These changes may be undesirable, such as changes during use, or desirable, as in biodegradation or deliberately lowering the molecular mass of a polymer. Such changes occur primarily because of the effect of these factors on the chemical composition of the polymer. Ozone cracking and UV degradation are specific failure modes for certain polymers. The susceptibility of a polymer to degradation depends on its structure. Epoxies and chains containing aromatic functionality are especially susceptible to UV degradation while polyesters are susceptible to degradation by hydrolysis. Carbon based polymers are more susceptible to thermal degradation than inorganically bound polymers such as Polydimethylsiloxane and are therefore not ideal for most high temperature applications.
Polymer degradation may occur through galvanic action. In 1990, Michael Faudree discovered that imide-linked resins in CFRP (carbon fiber reinforced polymers) composites degrade when bare composite is coupled with an active metal in saline, i.e. salt water environments.[36] Polymers affected include bismaleimides (BMI), condensation polyimides, triazines, and blends thereof. Degradation occurs in the form of dissolved resin and loose fibers. Hydroxyl ions are generated at the graphite cathode attacking the O-C-N bond in the polyimide structure. .This phenomenon, that polymers can undergo galvanic corrosion like metals do has been referred to as the "Faudree Effect". Standard corrosion protection procedures were found to prevent polymer degradation under most conditions.^ Mechanical Degradation of Dilute Polymer Solutions under Turbulent Flow,” C.A. Kim, J.T. Kim K. Lee, H.J. Choi and M.S. Jhon, Polymer 41(21), 7611-7615 (2000).
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

The degradation of polymers to form smaller molecules may proceed by random scission or specific scission. The degradation of polyethylene occurs by random scission—a random breakage of the linkages (bonds) that hold the atoms of the polymer together. When heated above 450 DEGC it degrades to form a mixture of hydrocarbons. Other polymers—like polyalphamethylstyrene—undergo specific chain scission with breakage occurring only at the ends. They literally unzip or depolymerize to become the constituent monomer.
.However, the degradation process can be useful from the viewpoints of understanding the structure of a polymer or recycling/reusing the polymer waste to prevent or reduce environmental pollution.^ "Controlling the Shear-Induced Structural Transition of Rod-like Micelles Using Nonionic Polymer" M. T. Truong; L. M. Walker, accepted Langmuir (July 2000) .
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

.Polylactic acid and polyglycolic acid, for example, are two polymers that are useful for their ability to degrade under aqueous conditions.^ Mechanical Degradation of Dilute Polymer Solutions under Turbulent Flow,” C.A. Kim, J.T. Kim K. Lee, H.J. Choi and M.S. Jhon, Polymer 41(21), 7611-7615 (2000).
  • Carnegie Mellon Polymer Science 10 January 2010 19:43 UTC www.chem.cmu.edu [Source type: Academic]

A copolymer of these polymers is used for biomedical applications, such as hydrolysable stitches that degrade over time after they are applied to a wound. These materials can also be used for plastics that will degrade over time after they are used and will therefore not remain as litter.
The sorting of polymer waste for recycling purposes may be facilitated by the use of the Resin identification codes developed by the Society of the Plastics Industry to identify the type of plastic.

Product failure

Chlorine attack of acetal resin plumbing joint
In a finished product, such a change is to be prevented or delayed. Failure of safety-critical polymer components can cause serious accidents, such as fire in the case of cracked and degraded polymer fuel lines. Chlorine-induced cracking of acetal resin plumbing joints and polybutylene pipes has caused many serious floods in domestic properties, especially in the USA in the 1990s. Traces of chlorine in the water supply attacked vulnerable polymers in the plastic plumbing, a problem which occurs faster if any of the parts have been poorly extruded or injection molded. Attack of the acetal joint occurred because of faulty molding, leading to cracking along the threads of the fitting which is a serious stress concentration.
Ozone-induced cracking in natural rubber tubing
Polymer oxidation has caused accidents involving medical devices. One of the oldest known failure modes is ozone cracking caused by chain scission when ozone gas attacks susceptible elastomers such as natural rubber and nitrile rubber. They possess double bonds in their repeat units which are cleaved during ozonolysis. Cracks in fuel lines can penetrate the bore of the tube and cause fuel leakage. If cracking occurs in the engine compartment, electric sparks can ignite the gasoline and can cause a serious fire.
Fuel lines can also be attacked by another form of degradation: hydrolysis. Nylon 6,6 is susceptible to acid hydrolysis, and in one accident, a fractured fuel line led to a spillage of diesel into the road. If diesel fuel leaks onto the road, accidents to following cars can be caused by the slippery nature of the deposit, which is like black ice.

See also

References

  1. ^ Y. Roiter and S. Minko (2005). "AFM Single Molecule Experiments at the Solid-Liquid Interface: In Situ Conformation of Adsorbed Flexible Polyelectrolyte Chains". Journal of the American Chemical Society 127 (45): 15688–15689. doi:10.1021/ja0558239. PMID 16277495. 
  2. ^ Painter, p. 1
  3. ^ McCrum, p. 1
  4. ^ Sperling, p. 10
  5. ^ Sperling, p. 11
  6. ^ Sperling, p. 15
  7. ^ S.A. Baeurle (2009). "Multiscale modeling of polymer materials using field-theoretic methodologies: a survey about recent developments". Journal of Mathematical Chemistry 46 (2): 363–426. doi:10.1007/s10910-008-9467-3. 
  8. ^ Sperling, p. 30
  9. ^ a b Rubinstein, p. 6
  10. ^ Campbell, Neil A.; Brad Williamson; Robin J. Heyden (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 0-13-250882-6. http://www.phschool.com/el_marketing.html. 
  11. ^ IUPAC; Kratochvíl, P.; Stepto, R. F. T.; Suter, U. W. (1996). "Glossary of Basic Terms in Polymer Science". Pure Appl. Chem. 68: 2287–2311. doi:10.1351/pac199668122287. 
  12. ^ Painter, pp. 96-100
  13. ^ a b Rubinstein, p. 5
  14. ^ McCrum, p. 37
  15. ^ McCrum, p. 30
  16. ^ Rubinstein, p. 3
  17. ^ McCrum, p. 33
  18. ^ Rubinstein, pp. 23-24
  19. ^ Painter, p. 22
  20. ^ Rubinstein, p. 50
  21. ^ a b Painter, p. 14
  22. ^ Painter, p. 15
  23. ^ Sperling, p. 47
  24. ^ "IUPAC Purple Book: Definition of terms relating to crystalline polymers (1988) See Sec.1.3 Degree of Crystallinity" (PDF). http://www.iupac.org/publications/books/pbook/PurpleBook-C4.pdf. 
  25. ^ Allcock, Harry R.; Lampe, Frederick W.; and Mark, James E. (2003). Contemporary Polymer Chemistry (3 ed.). Pearson Education. p. 546. ISBN 0130650560. 
  26. ^ Rubinstein, p. 13
  27. ^ Ashby, Michael and Jones, David (1996). Engineering Materials (2 ed.). Butterworth-Heinermann. pp. 191–195. ISBN 0750627662. 
  28. ^ M. A. Meyers and K. K. Chawla (1999). Mechanical Behavior of Materials. Cambridge University Press. p. 41. ISBN 978-0-521-86675-0. http://www.toodoc.com/Mechanical-Behavior-of-Materials-ebook.html. 
  29. ^ Brandrup, J.; Immergut, E.H.; Grulke, E.A. (1999). Polymer Handbook (4 ed.). Wiley-Interscience. ISBN 0471479365. 
  30. ^ CAS: Index Guide, Appendix IV ((c) 1998)
  31. ^ IUPAC (1976). "Nomenclature of Regular Single-Strand Organic Polymers". Pure Appl. Chem. 48: 373–385. doi:10.1351/pac197648030373. 
  32. ^ "Macromolecular Nomenclature Note No. 18". http://www.polyacs.org/nomcl/mnn18.html. 
  33. ^ U.S. Patent 6,052,184 and U.S. Patent 6,653,150, other patents pending
  34. ^ F. H. Florenzano; R. Strelitzki; W. F. Reed (1998). "Absolute, Online Monitoring of Polymerization Reactions". Macromolecules 31 (21): 7226–7238. doi:10.1021/ma980876e. 
  35. ^ A. M. Alb; M. F. Drenski; W. F. Reed (2008). "Implications to Industry: Perspective. Automatic continuous online monitoring of polymerization reactions (ACOMP)". Polymer International 57: 390–396. doi:10.1002/pi.2367. 
  36. ^ M.C. Faudree, Relationship of Graphite/Polyimide Composites to Galvanic Processes (1991). Society for the Advancement of Material and Process Engineering (SAMPE) Journal 2: 1288–1301. 

Bibliography

  • Cowie, J.M.G. Polymers: Chemistry and Physics of Modern Materials, Blackie (in USA: Chapman and Hall), 2nd edition (1991).
  • Ezrin, Meyer. Plastics Failure Guide: Cause and Prevention, Hanser-SPE (1996).
  • Lewis, Peter Rhys; Reynolds, K.; and Gagg, C. Forensic Materials Engineering: Case studies, CRC Press (2004).
  • McCrum N. G., Buckley C. P., Bucknall C. B., Principles of Polymer Engineering, Oxford University Press, 1997 ISBN 9780198565260
  • Painter P. C., Coleman M. M., Fundamentals of Polymer Science: an Introductory Text, CRC Press, 1997 ISBN 1566765595
  • Rubinstein, M. and Colby, R., Polymer Physics, Oxford University Press, 2006 ISBN 019852059X
  • Sperling L. H., Introduction to Physical Polymer Science, Wiley & Sons, 2006 ISBN 047170606X
  • Wright, David C. Environmental Stress Cracking of Plastics, RAPRA (2001).

External links


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also polymer

Contents

German

Noun

Polymer n. (genitive Polymers, plural Polymere)
  1. polymer

Declension

singular
nominative Polymer
genitive Polymers
dative Polymer
accusative Polymer

Related terms


Simple English

A polymer is a molecule, made from joining together many small molecules called monomers. The word "polymer" can be broken down into "poly" (meaning "many" in Greek) and "mer" (meaning "unit"). This shows how the chemical composition of a polymer consists of many smaller units (monomers) bonded together into a larger molecule. A chemical reaction bonding monomers together to make a polymer is called polymerization.

Some polymers are natural. Proteins have polypeptide molecules, which are natural polymers made from various amino acid monomer units. Nucleic acids are huge natural polymers made up of millions of nucleotide units. Cellulose and starch (two types of carbohydrate) are also natural polymers made up of glucopyranose monomer bonded together in different ways. Some polymers are man-made. Plastics, rubber, and fibers are made up of polymers.

Make up of polymers

If the "units" called monomers in a polymer are all the same, then the polymer is called a "homopolymer". Homopolymers are named by adding the prefix poly- before the monomer name from which the polymer is made. For example, a polymer made by bonding styrene monomer molecules together is called polystyrene.

molecules join together to make a polystyrene molecule.  The squiggly lines at both ends of the polymer mean that just a short section of a long molecule is shown here. ]]

If the monomers are not all the same, the polymer is called a "copolymer" or a "heteropolymer".

]] Many polymer molecules are like chains where the monomer units are the links. Polymer molecules can be straight-chain, have branching from the main chain, or cross-linking between chains. As an example of cross-linking, sulfhydryl (-S-H) groups in two cysteine amino acid units in polypeptide chains can bond together to make a disulfide bridge (-S-S-) joining the chains together.


Citable sentences

Up to date as of December 13, 2010

Here are sentences from other pages on Polymer, which are similar to those in the above article.








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