Controlled Synthesis and Interface Properties of New Amphiphilic PCL-g-PEO Copolymers

Abstract

Novel biodegradable and biocompatible poly(ε-caprolactone)-graft-poly(ethylene oxide), PCL-g-PEO, copolymers consisting of biocompatible blocks have been synthesized by ring-opening copolymerization of ε-caprolactone (εCL) and a poly(ethylene oxide) (PEO) macromonomer, i.e., PEO end-capped by an ε-caprolactone unit (γPEO.CL). The control is effective on the composition and length of both the hydrophobic polyester backbone and the hydrophilic PEO grafts. The reactivity ratios have been determined by monitoring the copolymer composition in relation to the comonomer conversion. The PCL-g-PEO copolymers have a tapered (gradient) rather than a random structure consistent with r_εCL = 3.95 and r_γPEO.CL = 0.05. The amphiphilic graft copolymers display surfactant properties similar to those of PEO-b-PCL diblock copolymers of comparable composition and solubility, as supported by CHCl₃/water interfacial tension measured by the pendant drop method.