![]() Oxygen is also commonly present in polymer backbones, such as those of polyethylene glycol, polysaccharides (in glycosidic bonds), and DNA (in phosphodiester bonds). Many other structures do exist for example, elements such as silicon form familiar materials such as silicones, examples being Silly Putty and waterproof plumbing sealant. A simple example is polyethylene ('polythene' in British English), whose repeat unit or monomer is ethylene. Most commonly, the continuously linked backbone of a polymer used for the preparation of plastics consists mainly of carbon atoms. More than 330 million tons of these polymers are made every year (2015). The list of synthetic polymers, roughly in order of worldwide demand, includes polyethylene, polypropylene, polystyrene, polyvinyl chloride, synthetic rubber, phenol formaldehyde resin (or Bakelite), neoprene, nylon, polyacrylonitrile, PVB, silicone, and many more. A variety of other natural polymers exist, such as cellulose, which is the main constituent of wood and paper. Natural polymeric materials such as hemp, shellac, amber, wool, silk, and natural rubber have been used for centuries. Polymers are of two types: naturally occurring and synthetic or man made. Structure of a styrene-butadiene chain, from a molecular simulation. 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. Polyisoprene of latex rubber is an example of a natural polymer, and the polystyrene of styrofoam is an example of a synthetic polymer. ![]() An emerging important area now focuses on supramolecular polymers formed by non-covalent links. Historically, products arising from the linkage of repeating units by covalent chemical bonds have been the primary focus of polymer science. Polymers are studied in the fields of polymer science (which includes polymer chemistry and polymer physics), biophysics and materials science and engineering. 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. The term was coined in 1833 by Jöns Jacob Berzelius, though with a definition distinct from the modern IUPAC definition. The term "polymer" derives from the Greek word πολύς ( polus, meaning "many, much") and μέρος ( meros, meaning "part"). Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. 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. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Ī polymer ( / ˈ p ɒ l ɪ m ər/ Greek poly-, "many" + -mer, "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. A macromolecule is a molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. ![]() A polymer is a substance composed of macromolecules.
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