Copolymerization of ε‐caprolactone and morpholine‐2,5‐dione derivatives

Abstract

Abstract Novel biodegradable poly(ester‐amide)s were prepared by ring‐opening copolymerization of ε‐caprolactone and 3‐ and/or 6‐alkyl‐substituted morpholine‐2,5‐dione derivatives. The copolymerizations were carried out in the bulk using stannous octoate as an initiator. Molecular weights of the copolymers ranged from 1,0 · 10 4 to 8,3 · 10 4 and decreased with increasing mole fractions of morpholine‐2,5‐dione derivatives in the feed. 13 C NMR sequence analysis indicated that the copolymers had a random distribution of ε‐oxycaproyl and depsipeptide units, which resulted from the occurrence of transesterification reactions during copolymerization. The results of the DSC measurements and 13 C NMR sequence analysis showed a close relationship between the crystallinity and average length of ε‐oxycaproyl blocks. Copolymers with a mole fraction of depsipeptide units smaller than 0,20 were semi‐crystalline, whereas incorporation of larger amounts of depsipeptide units resulted in amorphous copolymers. The melting point depression as a function of the molar composition of the semi‐crystalline copolymers was in good agreement with the melting point depression predicted by the Baur equation, which indicated the rejection of depsipeptide units from crystals consisting of ε‐oxycaproyl units.