Polylactones. 13. Transesterification of Poly(<i>L</i>-Lactide) with Poly(Glycoude), Poly(β-Propio-Lactone), and Poly[ϵ -Caprolactone)

Abstract

Homogeneous blends of poly(L-lactide) (Mn = 30 000 to 40 000) and poly(β-propiolactone) or poly(ϵ-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°C. At 100°C, transesterification was barely detectable even after 96 h. When poly(β-propiolactone) was used as the reactant at 150°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). In the case of poly(ϵ-caprolactone), copolyesters with slightly blocky sequences were obtained with tributyltin methoxide as catalyst, whereas the acidic catalysts caused rapid degradation. The copolyesters were characterized by means of 1H-NMR spectroscopy with regard to their molar composition, by means of 13C-NMR spectroscopy with regard to their sequences, and by means of differential scanning calorimetry with regard to crystallinity.