NOVEL RING-OPENING POLYMERIZATION OF LACTIDE BY LIPASE

Six-membered D,L-, L,L- and D,D-lactides were polymerized by lipase ov er a temperature range of 80 to 130 degrees C to yield the polylactide with a molecular weight (M-w) of greater than 270000. Among the lipas es tested, lipase PS gave the greatest molecular weight of polylactide . The polymerization of D,L-lactide by lipase was better than that of L,L- and D,D-lactides. The polymerization of lactide by lipase showed the characteristic features, such as induction period for the initiati on of polymerization, formation of oligomer and subsequent formation o f high molecular weight polylactide, which may imply the characteristi c polymerization by lipase. Immobilization of lipase on celite signifi cantly enhanced the polymerization of lactide particularly with respec t to the low concentration of the enzyme and the M-w of the resultant polymer. It was found that there is no clear relationship between enzy matic polymerizability and enzymatic degradability with respect to the enzyme origin and the stereochemistry of lactide.