Tf. Al-azemi et Ks. Bisht, Novel functional polycarbonate by lipase-catalyzed ring-opening polymerization of 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one, MACROMOLEC, 32(20), 1999, pp. 6536-6540
Water-soluble polycarbonate having pendent carboxyl groups on the main-chai
n carbons is reported for the first time. This paper describes synthesis an
d enzyme-catalyzed ring-opening polymerization of a novel carbonate monomer
, 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (1). Various commercially a
vailable lipases were screened for their ability to polymerize 1 in bulk at
80 degrees C. Monomer conversion and molecular weight of the polymer were
significantly influenced by the source of the enzyme. For example, of the s
even Lipases screened, lipase AK (from Pseudomonas fluorescens) gave the hi
ghest monomer conversion (97%) and molecular weight (M-n = 6100). In reacti
ons carried out under identical experimental conditions, no polymerization
was observed when thermally deactivated lipase AK was used. Debenzylation o
f 2 by catalytic hydrogenation led to the corresponding linear polycarbonat
e, 3, with pendent carboxyl groups. Presence of pendent carboxyl groups is
expected to enhance the biodegradability of the polycarbonate and facilitat
e a variety of potential biomedical applications, e.g., as polymeric drug c
arriers in time-controlled drug delivery systems.