POLYLACTONES - 44 - POLYMERIZATIONS OF L-LACTIDE CATALYZED BY MANGANESE SALTS

Manganese(II)chloride, bromide, acetate and L-lactate were used as cat alysts for the polymerization of L-lactide. All polymerizations were p erformed in bulk and despite a high reaction temperature (150 degrees C), long reaction times (192 hours) were needed to achieve nearly comp lete conversions. Mn L-lactate was found to be the most reactive of th e four catalysts. Yet, relatively low molecular weights (M-v = 33 000) and partial racemization were found under all circumstances. Furtherm ore, copolymerizations of L-lactide and glycolide or L-lactide and eps ilon-caprolactone were studied. A few homopolymerizations of L-lactide catalyzed by magnesium lactate or calcium lactate were included for c omparison. These more basic initiators gave even worse results.