AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
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. Is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Ī polymer ( / ˈ p ɒ l ɪ m ər/ Greek poly-, "many" + -mer, "part") 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. Also new to this edition is a never-before-published, introductory essay by language commentator David Crystal on the History of English providing stimulating insight into the development of the English language.A polymer is a substance composed of macromolecules. Some of the new words included in this edition are Afrobeat, carbon-neutral, darknet, heaviosity, impactful, knuckle-dragger, nanomaterial, retro-futurist, smoosh, testosteronic, webinar, and thousands more. Now with 2,500 new words and meanings based on the ongoing research program of Oxford Dictionaries and the Oxford English Corpus, the Shorter is fresher than ever. The Shorter offers a historical and literary approach made famous by the OED, which no competitor can match. Each entry identifies a word's various meanings, origins, part of speech, pronunciation, and presents combinations in which the word is often found as well as cross-references to related words. It offers over 500,000 definitions covering virtually every word or phrase in use in the English language-worldwide-since 1700. No other dictionary comes close to the Shorter's range and depth. At a fraction of the price, the Shorter offers much of the same content, and provides the same quality of lexical excellence as its parent dictionary. If the 20-volume Oxford English Dictionary is the mother of all dictionaries, the Shorter is its most accomplished offspring. The sixth edition of the Shorter Oxford English Dictionary is updated, enlarged and enlivened with new words, new definitions, revised illustrative quotations-and a fully customizable CD-ROM.
0 Comments
Read More
Leave a Reply. |