Functionalization of poly(epsilon-caprolactone) by pendant hydroxyl, carboxylic acid and epoxide groups by atom transfer radical addition

A straightforward strategy is proposed for grafting hydroxyl, carboxylic acid and epoxide groups along poly (epsilon-caprolactone) chains. Statistical copolymerization of epsilon-caprolactone (epsilon-CL) with alpha-chloro-epsilon-caprolactone (alpha-Cl-epsilon-CL) has been initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP), followed by the atom transfer radical addition (ATRA) of but-3-en-1-ol, vinylacetic acid and 1,2-epoxyhex-5-ene, respectively, onto the alpha-chloro units of a poly(alpha-Cl-epsilon-CL-co-epsilon-CL) copolymer. alpha-Cl-epsilon-CL is easily prepared by the Baeyer-Villiger oxidation of 2-chlorocyclohexanone. The influence of the experimental conditions, i.e. temperature, solvent, catalyst, on the grafting yield has been discussed. Because ATRA is tolerant of the investigated functional groups, no protection/deprotection reaction is required, which is a major advantage of the method.