화학공학소재연구정보센터
Biomacromolecules, Vol.7, No.4, 1042-1048, 2006
Influence of PEG endgroup and molecular weight on its reactivity for lipase-catalyzed polyester synthesis
Polycondensations were performed at 70 degrees C in bulk using physically immobilized lipase B from Candida antaratica (CAL-B) as catalyst. Study of copolymerizations between sebacic acid and PEG diols of differing M,, values (200, 400, 600, 1000, 2000, and 10 000) showed that PEG 400 and 600 were most reactive (DPavg up to about 6). Increasing the PEG diol chain length from 600 to 1000, 2000, and 10 000 resulted in large decreases in copolymer DPavg values. PEG200 diacids (i.e., HOOC-(CH2)(x)-O-(CH2CH2O)(n)-(CH2)(x)-COOH) were successfully synthesized where x was 1, 4, 5, 7, 9, and 11. Study of copolymerizations of these diacids with 1,8-octanediol showed that, by introduction of a five-carbon methylene spacer (x = 5), remarkable increases in the reactivity of PEG200 diacids were achieved. In addition, introduction of this spacer was also effective for increasing the reactivity of PEG diacids of higher molecular weight (i.e., PEG400, 600, and 1000). This work verified the hypothesis that, by conversion of PEG chain ends to structures more closely resembling fatty acids, modified PEG building blocks are obtained that are better recognized as substrates by CAL-B during condensation reactions.