Triblock and pentablock copolymerizations of ε-caprolactone with l-lactide catalyzed by N-heterocyclic carbene

Abstract

Dihydroxyl capped biodegradable poly(ε-caprolactone)–poly(ethylene glycol)–poly(ε-caprolactone) (PCL–PEG–PCL) triblock copolymer and poly(L-lactide)–poly(ε-caprolactone)–poly(ethylene glycol)–poly(ε-caprolactone)–poly(L-lactide) (PLLA–PCL–PEG–PCL–PLLA) pentablock copolymer have been synthesized by using benzo-12-crown-4-imidazole carbene (B-12-C-4imY) as a catalyst, and PEG and PCL–PEG–PCL copolymer as macroinitiators, respectively. We focused on the influence of the varied reaction time, temperature and monomer/catalyst molar ratio on the copolymerizations. Chemical structures and physical properties of the block copolymers were studied through the characterization of ¹H, ¹³C NMR, GPC and DSC. The NMR spectral data of the copolymers displayed the chemical structures without random placement. Therefore, the pure triblock and pentablock copolymers have been synthesized successfully.