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

Water-soluble poly(γ-glutamic acid) (PGGA) esters were prepared by transesterification of poly(α-methyl-γ-glutamate) with mono-, di-, and triethylene glycols with one hydroxyl end group blocked as methyl ether. Only the monoglycol appeared to be crystalline with melting at 160°C, and glass-transition temperatures were found to increase from 10 to 60°C with the length of the oxyethylene side chain. All these poly(γ-glutamate)s are stable up to temperatures near 250°C. Moisture sorption, surface wettability, and hydrodegradability were evaluated as a function of time. It was found that in overall sensitivity to water increased with the glycol chain length but the behavior at short contact times was critically affected by conformational factors. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2027–2036, 2001