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](PIB MD, A) and poly(ethylene oxide) ((M) over bar(n) = 6000, PEO, B) blocks, PI BMD-b-PEO-b-PIBMD, were synthesised via ring-opening polymerization of 3(S) -isobutyl-morpholine-2,5-dione in the presence of hydroxytelechelic poly(et hylene oxide) with stannous octoate as a catalyst. These block copolymers m ay find applications in cell encapsulation and in drug delivery. (M) over b ar(n) of the resulting copolymers increases with increasing 3(S)-isobutyl-m orpholine-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 tak es 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 homop olymer, and the crystallinity of the PEO block decreases with increasing le ngth of the PIBMD blocks. The PIBMD block crystallizes first upon cooling f rom the melt. This leads to only imperfect crystallization or no crystalliz ation of the PEO blocks.