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Step-growth polymers increase in molecular weight at a very slow rate at lower conversions and reach moderately high molecular weights only at very high conversion (i.e., >95%). Solid state polymerization to afford polyamides (e.g., nylons) is an example of step-growth polymerization.
They differ in their properties according to their chemical composition (homo-or copolyester, contained hydroxy fatty acids). They are UV stable, in contrast to other bioplastics from polymers such as polylactic acid, partial ca. temperatures up to 180 °C, and show a low permeation of water.
The newly formed nucleophile will then attack the atom X in another monomer molecule, and the sequence would repeat until the polymer is formed. [20] Anionic ring-opening polymerizations (AROP) involve nucleophilic reagents as initiators. Monomers with a three-member ring structure - such as epoxides, aziridines, and episulfides - undergo ...
Molecular weights of 130 kDa can be obtained this way. Even higher molecular weights can be attained by carefully crystallizing the crude polymer from the melt. Carboxylic acid and alcohol end groups are thus concentrated in the amorphous region of the solid polymer, and so they can react. Molecular weights of 128–152 kDa are obtainable thus ...
Polycondensation of glycolic acid is the simplest process available to prepare PGA, but it is not the most efficient because it yields a low molecular weight product. Briefly, the procedure is as follows: glycolic acid is heated at atmospheric pressure and a temperature of about 175 to 185 °C is maintained until water ceases to distill ...
In 1996, Monsanto (who sold PHB as a copolymer with PHV) bought all patents for making the polymer from ICI/Zeneca including the trademark "Biopol". [5] However, Monsanto's rights to Biopol were sold to the American company Metabolix in 2001 and Monsanto's fermenters producing PHB from bacteria were closed down at the start of 2004.
The functional properties of CMC depend on the degree of substitution of the cellulose structure (i.e., how many of the hydroxyl groups have been converted to carboxymethylene groups in the substitution reaction), as well as the chain length of the cellulose backbone structure and the degree of clustering of the carboxymethyl substituents.
General chemical structure of an alkyl polyglucoside, a common form of alkyl polyglycoside. Alkyl polyglycosides (APGs) are a class of non-ionic surfactants widely used in a variety of cosmetic, household, and industrial applications. Biodegradable and plant-derived from sugars, these surfactants are usually derivatives of glucose and fatty ...