Biodegradable multiblock copolyesters prepared from ε-caprolactone, L-lactide, and trimethylene carbonate by means of bismuth hexanoate

Telechelic random copolymers were prepared by copolymerization of epsilon-caprolactone (epsilon CL) and trimethylene carbonate (TMC) in bulk using bismuth(III) hexanoate, Bi(OHex)(3), as initiator. These copolymers were characterized by H-1 and C-13 NMR spectroscopy. A-B-A triblock copolymers were synthesized by chain extension of these random copolymers with L-lactide, whereby the chain length of the amorphous central blocks and of the crystalline poly(L-lactide) blocks were varied. Finally, the triblock copolymers were transformed into multiblock copolymers by chain extension with 1,6-hexamethylenediisocyanate. All three synthetic steps were performed in a one-pot-procedure. The resulting multiblock copolymers were characterized by H-1 NMR spectroscopy, SEC measurements, DSC measurements, and stress-strain measurements. Typical mechanical properties of thermoplastic elastomers were detected.