This work was directed at extending the use of lipase-catalyzed ring-o
pening polymerizations to cyclic carbonate monomers. Of the seven lipa
ses screened for bulk trimethylene carbonate (TMC) polymerization (70
degrees C, 120 h), Novozym-435 from Candida antarctica gave almost qua
ntitative monomer conversion (97%) and poly(TMC) with a M-n = 15 000 (
M-w/M-n = 2.2) with no apparent decarboxylation during propagation. Th
e lipases from Pseudomonas species (AK and PS-30) and porcine pancreas
(PPL) also exhibited high monomer conversions (>80%, 120 h) but gave
lower molecular weight polymers with broad polydispersity. Analyses by
H-1-NMR spectroscopy suggested that poly(TMC) prepared by Novozym-435
-catalyzed polymerization had terminal -CH2OH functionalities at both
chain ends. A monotonic increase in monomer conversion with time and t
he rapid increase in M,, as a function of monomer conversion for Novoz
ym-435-catalyzed TMC bulk polymerization at 70 degrees C suggest that
the polymerization has chain-type propagation kinetics. An increase in
conversion above 66% did not substantially change M-n. The percent co
nversion was larger when the reaction temperature was increased from 4
5 to 55 degrees C. Further increase in the reaction temperature from 5
5 to 85 degrees C did not give higher percent conversion values. The m
olecular weight decreased substantially as the reaction temperature wa
s increased from 55 to 85 degrees C (M-n from 24 400 to 5 900). The hi
ghest poly(TMC) molecular weight (M-n = 24 400) was obtained by conduc
ting the polymerization at 55 degrees C. Monomer conversion and molecu
lar weight as a function of the percent reaction water content (w/w) w
ere investigated. Increasing the water content resulted in enhanced po
lymerization rates and decreased molecular weights. Separation of the
oligomeric products from polymerizations of TMC in dried dioxane and t
oluene catalyzed by porcine pancreatic lipase led to the isolation of
di- and triadducts of trimethylene carbonate. Based on the symmetrical
structure of these products and the end-group structure of high molec
ular weight chains, a mechanism for chain initiation and propagation f
or lipase-catalyzed TMC polymerization was proposed.