Molecular weight aliphatic polyesters

Minnick, L. A., Reinforced molding composition based on poly(l,4-cyclohexylenedimethylene terephthalate) containing a high molecular weight aliphatic polyester, US Patent 5 242 967, 1992. 

Polyesters and polyamides are the most prevalent of this type of polymer. Poly(ethylene terephthalate) is used in bottle manufacture and along with other packaging plastics is not biodegradable. Potts(54) established very early that only low melting and low molecular weight aliphatic polyesters were biodegradable. 

Completely aliphatic polyesters, made from aliphatic diacid and aliphatic diol components), are not of major industrial importance because of their low melting temperatures and poor hydrolytic stability. (Low-molecular-weight aliphatic polyesters are used as plasticizers and prepolymer reactants in the synthesis of polyurethanes see Secs. 2-12e, 2-13c-2). 

According to O. Bayer, the latter procedure, which is used especially for the preparation of elastomeric polyurethanes, is carried out in two separate stages. First, a carefully dried, relatively low-molecular-weight, aliphatic polyester or polyether with hydroxy end groups is reacted with an excess of diisocyanate. A chain extension reaction occurs in which two to three linear diol molecules are coupled with diisocyanate, so as to yield a linear polymer with some in-chain urethane groups and with isocyanate end groups. 

The ring-opening reaction can be performed either as a bulk polymerization, or in solution, emulsion, or dispersion [15,16]. A catalyst or initiator is necessary to start the polymerization. Under rather mild conditions, high-molecular weight aliphatic polyesters of low polydispersity can be prepared in short periods of time. Problems associated with condensation polymerization, such as the need for exact stoichiometry, high reaction temperatures, and the removal of low molecular weight by-products (e.g., water) are excluded in ROP [17]. 

Albertsson, A.-C. Srivastava, R.K. High molecular weight aliphatic polyesters from enzyme-catalyzed ring-opening polymerization and their use ACS Polymer Preprints, 2006, 7(2), 245. 

Shrrahama H., Kawaguchi Y, Aludin M.S., Yasuda H. Synthesis and enzymatic degradation of high molecular weight aliphatic polyesters, J. Appl. Polym. Sci. 80 (2001) 340. 

PCT displays a high deflection temperature (HDT) consistent with its high melting point which enables it to be used in glass-fiber reinforced formulations resistant to elevated temperatures. Usual formulations for injection molding contain 30-40 % of glass fiber as well as other additives, such as low molecular weight aliphatic polyesters, in order to increase the crystalizability of PCT. In some applications, thermal stabilizers and flame retardant bromide and antimony aromatic derivatives are also added (14,118). 

In contrast to the limitations of the step-growth polymerization techniques, ring-opening polymerization (ROP) of cyclic esters may provide high-molecular-weight aliphatic polyesters (up to lOOkgmol" ) under mild conditions. " ROP is the prefened synthetic pathway used in industry, and... 

Since Potts had shown that low molecular weight aliphatic polyesters were the only general class of synthetic polymers that were biodegradable, it appeared the copolymers with the cyclic ketene acetals with various monomers should lead to copolymers that were really polyesters and therefore should be biodegradable. Thus, the copolymerization of the cyclic ketene acetal 1 produced a series of copolymers that were in fact polyesters, but with physical properties very similar to polyethylene. 

Aliphatic polyesters are a group of synthesized homopolymers or copolymers. They are nontoxic and can easily be fabricated into a variety of novel devices, such as rods, screws, nails, and cylinders. The polymers are commercially available in varying molecular weights as both homopolymers and copolymers. Molecular weights of polyesters range from 2000 to greater than 100000. 

Among the high molecular weight aliphatic-aromatic polyesters, the highest commercial volume material is poly(ethylene terephthalate). Most of it is prepared from dimethylene terephtha-late and ethylene glycol by a transesterification reaction ... 

Most polyesters, polyamides, and polyurethanes are susceptible to hydrolysis with a consequent decrease in molecular weight. Aliphatic polymers often hydrolyze more rapidly than aromatic polymers. Once again, the lower molecular-weight materials are subject to biological attack. The hydrolysis itself may be part of enzymatic attack on the main chains. Some polyurethanes based on polyester polyols are easily... 

Polyesters were initially discovered and evaluated ia 1929 by W. H. Carothers, who used linear aliphatic polyester materials to develop the fundamental understanding of condensation polymerisation, study the reaction kinetics, and demonstrate that high molecular weight materials were obtainable and could be melt-spun iato fibers (1 5). 

Phthalazinone, 355 synthesis of, 356 Phthalic anhydride, 101 Phthalic anhydride-glycerol reaction, 19 Physical properties. See also Barrier properties Dielectric properties Mechanical properties Molecular weight Optical properties Structure-property relationships Thermal properties of aliphatic polyesters, 40-44 of aromatic-aliphatic polyesters, 44-47 of aromatic polyesters, 47-53 of aromatic polymers, 273-274 of epoxy-phenol networks, 413-416 molecular weight and, 3 of PBT, PEN, and PTT, 44-46 of polyester-ether thermoplastic elastomers, 54 of polyesters, 32-60 of polyimides, 273-287 of polymers, 3... 

Schindler, A., Hibionada, Y. M., and Pitt, C. G., Aliphatic polyesters III. Molecular weight and molecular weight distribution in alcohol-initiated polymerization of e-caprolactone, J. Polym. Sci., Part A Polym. Chem., 20. 319-326, 1982. 

Enzymatic synthesis of aliphatic polyesters was also achieved by the ringopening polymerization of cyclic diesters. Lactide was not enzymatically polymerized under mild reaction conditions however, poly(lacfic acid) with the molecular weight higher than 1 x 10" was formed using lipase BC as catalyst at higher temperatures (80-130°C). Protease (proteinase K) also induced the polymerization however, the catalytic activity was relatively low. 

The enzymatic synthesis of polyesters from activated diesters was achieved under mild reaction conditions. The polymerization of bis(2,2,2-trichloroethyl) glutarate and 1,4-butanediol proceeded in the presence of PPL at room temperature in diethyl ether to produce the polyesters with molecular weight of 8.2 x 10. Vacuum was applied to shift the equilibrium forward by removal of the activated alcohol formed, leading to the production of high molecular weight polyesters. The polycondensation of bis(2,2,2-trifluoroethyl) sebacate and aliphatic diols took place using lipases BC, CR, MM, and PPL as catalyst in diphenyl ether. Under the... 

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