condensation reaction leads to the production of polymers.
what type of reaction leads to the production of polymers?
condensation reaction
the history of human use of polymers has been long since the mid-19th century, when it entered the chemical modification of natural polymers, 1839 c. goodyear has found a critical advance in the research of rubber vulcanization, which has turned natural rubber into a practical engineering material. in 1870, j. w. hyatt uses camphor to plasticize nitrocellulose to make nitrocellulose plastics industrial. 1907 l. baekeland reported the synthesis of the first thermosetting phenolic resin, which was industrialized in the 1920s, the first synthetic plastic product. in 1920, h. standinger proposed that polymers are long-chain molecules that are connected by structural units through common covalent bonds. this conclusion laid the foundation for the establishment of modern polymer science. subsequently, carothers divided the synthetic polymers into two broad categories, namely a polycondensate obtained by a polycondensation reaction and an addition polymer obtained by a polyaddition reaction. 1950s k. ziegler and g. natta discovered a coordination polymerization catalyst and pioneered the era of synthesis of stereoregular polymers. in the decades after the establishment of the concept of macromolecules, the synthesis of high polymers has achieved rapid development, and many important polymers have been industrialized one after another.
polymer engineering
the condensed tannins can nevertheless undergo acid-catalyzed cleavage in the presence of (an excess of) a nucleophile like phloroglucinol (reaction called phloroglucinolysis), benzyl mercaptan (reaction called thiolysis), thioglycolic acid (reaction called thioglycolysis) or cysteamine. these techniques are generally called depolymerisation and give information such as average degree of polymerisation or percentage of galloylation. these are sn1 reactions, a type of substitution reaction in organic chemistry, involving a carbocation intermediate under strongly acidic conditions in polar protic solvents like methanol. the reaction leads to the formation of free and derived monomers that can be further analyzed. the free monomers correspond to the terminal units of the condensed tannins chains. if thiolysis is done directly on plant material (rather than on purified tannins), it is, however, important to subtract naturally occurring free flavanol monomers from the concentration of terminal units that are released during depolymerisation.
condensed tannin