New biomaterial:: triblock copolymers of poly [3(S)-isobutyl-morpholine-2,5-dione]-poly(ethylene oxide)

ABA-type block copolymers with poly[3(S)-isobutyl-morpholine-2,5-dione](PIBMD, A) and poly(ethylene oxide) ((M) over bar(n) = 6000, PEO, B) blocks, PIBMD-b-PEO-b-PIBMD, were synthesised via ring-opening polymerization of 3(S)-isobutyl-morpholine-2,5-dione in the presence of hydroxytelechelic poly(ethylene oxide) with stannous octoate as a catalyst. These block copolymers may find applications in cell encapsulation and in drug delivery. (M) over bar(n) of the resulting copolymers increases with increasing 3(S)-isobutyl-morpholine-2,5-dione content in the feed at constant molar ratio of monomer (M) to catalyst (C) (M/C = 125). No racemization of the leucine residue takes place during both homopolymerization of IBMD and polymerization of IBMD in the presence of 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 temperature of the PEO blocks is lower than that of the homopolymer, and the crystallinity of the PEO block decreases with increasing length of the PIBMD blocks. The PIBMD block crystallizes first upon cooling from the melt. This leads to only imperfect crystallization or no crystallization of the PEO blocks.