Water-soluble esters of biosynthetic poly(gamma-glutamic acid)

Water-soluble poly(gamma -glutamic acid) (PGGA) esters were prepared by tra nsesterification of poly(alpha -methyl-gamma -glutamate) with mono-, di-, a nd triethylene glycols with one hydroxyl end group blocked as methyl ether. Only the monoglycol appeared to be crystalline with melting at 160 degrees C, and glass-transition temperatures were found to increase from 10 to 60 d egreesC with the length of the oxyethylene side chain. All these poly(gamma -glutamate)s are stable up to temperatures near 250 degreesC. Moisture sor ption, surface wettability, and hydrodegradability were evaluated as a func tion of time. It was found that in overall sensitivity to water increased w ith the glycol chain length but the behavior at short contact times was cri tically affected by conformational factors. (C) 2001 John Wiley & Sons, Inc .