A polymer (〔(【引用サイトリンク】url=http://www.thefreedictionary.com/polymer )〕〔(【引用サイトリンク】url=http://dictionary.reference.com/browse/polymer )〕) (Greek ''poly-'', "many" + ''-mer'', "parts") is a large molecule, or macromolecule, composed of many repeated subunits. Because of their broad range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass relative to small molecule compounds produces unique physical properties, including toughness, viscoelasticity, and a tendency to form glasses and semicrystalline structures rather than crystals.
The term "polymer" derives from the ancient Greek word πολύς (''polus'', meaning "many, much") and μέρος (''meros'', meaning "parts"), and refers to a molecule whose structure is composed of multiple repeating units, from which originates a characteristic of high relative molecular mass and attendant properties.〔http://goldbook.iupac.org/M03667.html; accessed 7 October 2012. Per the IUPAC Gold Book and PAC sources referenced therein, "In many cases, especially for synthetic polymers, a molecule can be regarded as having a high relative molecular mass if the addition or removal of one or a few of the units has a negligible effect on the molecular properties." However, they note that the "statement fails in the case of certain macromolecules for which the properties may be critically dependent on fine details of the molecular structure."〕 The units composing polymers derive, actually or conceptually, from molecules of low relative molecular mass. The term was coined in 1833 by Jöns Jacob Berzelius, though with a definition distinct from the modern IUPAC definition.〔If two substances had empirical formulae that were integer multiples of each other – e.g., acetylene (C2H2) and benzene (C6H6) – Berzelius called them "polymeric". See: Jöns Jakob Berzelius (1833) "''Isomerie'', Unterscheidung von damit analogen Verhältnissen" (''Isomeric'', distinction from relations analogous to it), ''Jahres-Bericht über die Fortschitte der physischen Wissenschaften …'', 12 : 63–67. (From page 64 ): "Um diese Art von Gleichheit in der Zusammensetzung, bei Ungleichheit in den Eigenschaften, bezeichnen zu können, möchte ich für diese Körper die Benennung ''polymerische'' (von ''πολυς'' mehrere) vorschlagen." (In order to be able to denote this type of similarity in composition (is accompanied ) by differences in properties, I would like to propose the designation "polymeric" (from ''πολυς'', several) for these substances.)
Originally published in 1832 in Swedish as: Jöns Jacob Berzelius (1832) "Isomeri, dess distinktion från dermed analoga förhållanden," ''Årsberättelse om Framstegen i Fysik och Kemi'', pages 65–70 ; the word "polymeriska" appears on (page 66 ).〕 The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, who spent the next decade finding experimental evidence for this hypothesis.
Polymers are studied in the fields of biophysics and macromolecular science, and polymer science (which includes polymer chemistry and polymer physics). Historically, products arising from the linkage of repeating units by covalent chemical bonds have been the primary focus of polymer science; emerging important areas of the science now focus on non-covalent links. Polyisoprene of latex rubber and the polystyrene of styrofoam are examples of polymeric natural/biological and synthetic polymers, respectively. In biological contexts, essentially all biological macromolecules—i.e., proteins (polyamides), nucleic acids (polynucleotides), and polysaccharides—are purely polymeric, or are composed in large part of polymeric components—e.g., isoprenylated/lipid-modified glycoproteins, where small lipidic molecule and oligosaccharide modifications occur on the polyamide backbone of the protein.
The simplest theoretical models for polymers are ideal chains.
Polymers are of two types:
*Natural polymeric materials such as shellac, amber, wool, silk and natural rubber have been used for centuries. A variety of other natural polymers exist, such as cellulose, which is the main constituent of wood and paper.
*The list of synthetic polymers includes synthetic rubber, phenol formaldehyde resin (or Bakelite), neoprene, nylon, polyvinyl chloride (PVC or vinyl), polystyrene, polyethylene, polypropylene, polyacrylonitrile, PVB, silicone, and many more.
Most commonly, the continuously linked backbone of a polymer used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene ('polythene' in British English), whose repeating unit is based on ethylene monomer. 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. Oxygen is also commonly present in polymer backbones, such as those of polyethylene glycol, polysaccharides (in glycosidic bonds), and DNA (in phosphodiester bonds).
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