Synthesis and characterization of new ABA triblock copolymers with poly[3(S)-isobutylmorpholine-2,5-dione] and poly(ethylene oxide) blocks

ABA type block copolymers with poly[3(S)-isobutylmorpholine-2,5-dione] (PIB MD, A) and poly(ethylene oxide) ((M) over bar(n) = 6000, PEO, B) blocks, PI BMD-b-PEO-b-PIBMD, were synthesized via ring-opening polymerization of 3(S) -isobutylmorpholine-2,5-dione in the presence of hydroxytelechelic poly(eth ylene oxide) with stannous octoate as a catalyst. (M) over bar(n) of the re sulting copolymers increases with increasing 3(S)-isobutylmorpholine-2,5-di one content in the feed at constant mole ratio of monomer (M) to catalyst ( C) (M/C = 125). No racemization of the leucine residue takes place during b oth homopolymerization of IBMD and polymerization of IBMD in the presence o f PEO and Sn(Oct)(2). The melting temperature of the PIBMD segments in the block copolymers depends on the length of the PIBMD blocks. The melting tem perature of the PEO blocks is lower than that of the; homopolymer, and the crystallinity of the PEO block decreases with increasing length of the PIBM D blocks. The PIBMD block crystallizes first upon cooling from the melt. Th is leads to only imperfect crystallization or no crystallization of the PEO blocks.