Complex, degradable polyester materials via ketoxime ether-based functionalization: Amphiphilic, multifunctional graft copolymers and their resulting solution-state aggregates

Degradable, amphiphilic graft copolymers of poly(epsilon-caprolactone)-graft-poly(ethylene oxide), PCL-g-PEO, were synthesized via a grafting onto strategy taking advantage of the ketones presented along the backbone of the statistical copolymer poly(epsilon-caprolactone)-co-(2-oxepane-1,5-dione), (PCL-co-OPD). Through the formation of stable ketoxime ether linkages, 3 kDa PEO grafts and p-methoxybenzyl side chains were incorporated onto the polyester backbone with a high degree of fidelity and efficiency, as verified by NMR spectroscopies and GPC analysis (90% grafting efficiency in some cases). The resulting block graft copolymers displayed significant thermal differences, specifically a depression in the observed melting transition temperature, T-m, in comparison with the parent PCL and PEO polymers. These amphiphilic block graft copolymers undergo self-assembly in aqueous solution with the P(CL-co-OPD-co-(OPD-g-PEO)) polymer forming spherical micelles and a P(CL-co-OPD-co-(OPD-g-PEO)-co-(OPD-g-pMeOBn)) forming cylindrical or rod-like micelles, as observed by transmission electron microscopy and atomic force microscopy. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3553-3563, 2010