DEVELOPMENT OF NEW BIODEGRADABLE POLYMERS

In this work, we have synthesized the copolymers of a new optically ac tive lactone {(R)- or (S)-3-methyl-4-oxa-6-hexanolide (MOHEL), which c orresponds to the lactone derived from 3-hydroxybutyric acid (3HB) and ethylene glycol} with cyclic esters {epsilon-caprolactone (CL), delta -valerolactone (VL), beta-propiolactone (PL), and L-lactide (LA)}, the copolymer of the cyclic carbonate {2,2-dimethyltrimethylene carbonate (DTC)} with CL or LA, and the homopolymers of these monomers using ge neral ionic catalysts (AlEt(3)-H2O etc.) or an organolanthanide comple x catalyst. First, we have measured some properties (such as thermal p roperties) of the above polymers, then we investigated the biodegradab ility of the polymers by activated sludge, seawater, and enzymes. Amon g the polymers examined, it was the (R)-MOHEL/CL copolymer (especially the copolymer containing CL unit more than 50 mol%) that was degraded significantly under every degradation condition. The biodegradability of the polymers was strongly dependent not only on the chemical struc tures and properties of the polymers themselves such as optical activi ty, molecular weight, melting point, and crystallinity, but also on th e substrate specificity of exoenzymes. The H-1 NMR and mass spectrosco pic analyses for the products of (R)-MOHEL/CL (=15/85) copolymer degra ded by esterase revealed that most of the copolymer was ultimately deg raded into the hydroxy acid of CL (viz., 6-hydroxycaproic acid).