Synthesis and characterization of polylactide-block-polyisoprene-block-polylactide triblock copolymers: New thermoplastic elastomers containing biodegradable segments

Anionic polymerization of isoprene initiated by an alkyl lithium containing a silyl ether protected hydroxyl functionality followed by termination with ethylene oxide gave α,ω-functionalized polyisoprene with narrow molecular weight distribution and prescribed molecular weight in high yield. Deprotection resulted in α,ω-hydroxyl polyisoprene (HO-PI-OH) that was reacted with triethylaluminium to form the corresponding aluminium alkoxide macroinitiator. The macroinitiator was used for the controlled polymerization of lactide to yield polylactide-block-polyisoprene-block-polylactide triblock copolymers with narrow molecular weight distributions and free of homopolymer (HO-PI-OH) contamination. Microphase separation in these novel triblock copolymers was confirmed by SAXS and DSC.