POLYLACTONES .13. TRANS-ESTERIFICATION OF POLY(L-LACTIDE) WITH POLY(GLYCOLIDE), POLY(BETA-PROPIOLACTONE), AND POLY(EPSILON-CAPROLACTONE)

Homogeneous blends of poly(L-lactide) (M//n OVER BAR equals 30,000 to 40, 000) and poly( beta -propiolactone) or poly( epsilon -caprolactone) were prepared in solution. The solvent-free blends were subjected to transesterification catalyzed by means of methyl triflate, triflic acid, boron trifluoride, or tributyltin methoxide at 100 or 150 degree C. At 100 degree C, transesterification was barely detectable even after 96 h. When poly( beta -propiolactone) was used as the reactant at 150 degree C, degradation was faster than transesterification regardless of the catalyst. The same negative result was obtained for heterogeneous blends of poly(L-lactide) and poly(glycolide).