Novel functionalization routes of poly(ε-caprolactone)

The aluminum alkoxide mediated ring opening polymerization of functional lactones, such as γ-ethylene ketal-ε-caprolactone (TOSUO), γ-(triethylsilyloxy)-ε-caprolactone (SCL) and γ-bromo-ε-caprolactone (γBrCL), is a versatile route to polyesters containing ketal, ketone, alcohol and bromide groups. As result of living polyaddition mechanism, random and block copolymerization of εCL and γBrCL has been successfully carried out. The reactivity ratios are quite similar (1.08 for ε-CL, and 1.12 for γBrCL). These random copolymers are semicrystalline when they contain less than 30 mol% of γBrCL, otherwise they are amorphous. No transesterification reaction occurs during the sequential polymerization of ε-CL and γBrCL leading to block copolymers. Reaction of poly(εCL-co-γBrCL) with pyridine provides quantitatively a polycationic polyester. Furthermore, the reaction of this random copolymer with l,8-diazabicyclo[5.4.0] undec-7-ene (DBU) is a route to unsaturated polyesters, whose the non conjugated double bonds can be quantitatively converted into epoxides by reaction with m-chloroperbenzoic acid (mCPBA). No chain degradation is detected during these derivatization reactions of poly (εCL-co-γBrCL).