Nature s polymers

Nature s polymer chemistry has selected two basic molecular building blocks for fibrous products. 

These designations, of course, substantially simplify the total materials technology practiced during those periods. Man also made substantial use of nature s polymers In the form of wood, leather, bone, horn, shell, animal ligaments and tissues to make tools, clothing, houses, vehicles and weapons. 

The word protein comes from the Greek word proteios, meaning of first importance. Proteins have a wide range of biological functions, and thus they are involved in almost every biochemical process. We will start with the 20 monomers that are the building blocks of proteins, one of nature s polymers. We will then develop protein structure. 

Lenzing Fibers Cellulose-Nature s Polymer, http //www.lenzing.com/Jilead min/ template/pdf/nonwoven fibers/ presseinformationen/Vorschau LCA.pdf (accessed 4 April 2013). 

S.C. Moldoveanu, Analytical Pyrolysis of Natural Organic Polymers, Elsevier, Amsterdam (1998). 

It is of note that the arrival of Mark into the Du Pont sphere of influence coincided with the emergence of a midwestern bred and trained chemist, Wallace H. Carothers, as director of Du Pont s polymer research. The work associated with Mark and Carothers signaled the break from the empirical practice of polymer chemistry and the birth of the science of polymers. Carothers directed the research group which on October 27, 1938 publicly announced the synthesis of a synthetic polymer which, for the first time in history, had properties superior to natural fibers. The polymer was nylon. 

The polymer chapters tend to be long. There s a lot to cover under each topic. As a matter of fact, before you get to read about the polymers in Chapters 23 and. 24, you need to read about the nature of polymers in Chapter 22. It s a big body of chemistry and chemical engineering, but these chapters should give you a handle on it. 

Most naturally occurring polymers are largely homopolymers, but proteins and nucleic acids are copolymers composed of a number of different mers. While many synthetic polymers are homopolymers, the most widely used synthetic rubber, SBR, is a copolymer of styrene (S) and butadiene (B), with the R representing rubber. There are many other important copolymers. Here we will restrict ourselves to vinyl-derived copolymers. 

Among the naturally occurring filler materials are cellulosics such as wood flour, a-cellulose, shell flour, and starch, and proteinaceous fillers such as soybean residues. Approximately 40,000 t of cellulosic fillers are used annually by the U.S. polymer industry. Wood flour, which is produced by the attrition grinding of wood wastes, is used as filler for phenolic resins, urea resins, polyolefins, and PVC. Shell flour, which lacks the fibrous structure of wood flour, has been used as a replacement for wood flour for some applications. 

Some naturally occurring polymers such as cellulose, starch, wool, and silk are classified as condensation polymers, since one can postulate their synthesis from certain hypothetical reactants by the elimination of water. Thus cellulose can he thought of as the polyether formed by the dehydration of glucose. Carothers included such polymers by defining condensation polymers as those in which the formula of the repeating unit lacks certain atoms that are present in the monomer(s) from which it is formed or to which it may be degraded. In this... 

The first product that DuPont commercialized was polyamide, to which they gave the trademark Nylon. These polymers can be made from a diamine and a diacid or from an amino acid (the silk spider). (Remember that proteins are just polypeptides, which are polyamides formed from atnino acids so the DuPont scientists were only adapting and scaling up nature s process.)... 

Proteins are nature s polyamide condensation polymers. A protein is formed by polymerization of o-artiino acids, with the amino group on the carbon atom next to the carboxylic acid. Biologists call the bond formed a peptide rather than an amide. In the food chain these amino acids are continuously hydrolyzed and polymerized back into polymers, which the host can use in its tissues. These polymerization and depolymerization reactions in biological systems are all controlled by enzyme catalysts that produce extreme selectivity to the desired proteins. 

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