SYNTHESIS AND CHARACTERIZATION OF POLY(ε-CAPROLACTONE) BEARING PENDANT FUNCTIONAL GROUPS

Biodegradable aliphatic polyesters such as poly (glycolide) (PGA), poly(L-lactide) (PLA), poly (epsilon-caprolactone) (PCL) and their copolymers have been found widely applications in sutures, tissue engineering, bone fixation and controlled drug delivery due to their excellent biocompatible and biodegradable properties. But the shortage of functional pendant groups and low hydrophilicity limited their further applications. In this work, we explored a synthetic strategy of aliphatic polyesters functionalized with the pendant carboxylic groups through the ring-opening polymerization of novel functionalized lactone. First, 2-ethoxycarbonylmethyl-cyclohexanone was synthesized via nucleophilic addition. Second, 6-ethoxycarbonylmethyl-epsilon-caprolactone (ECL) was generated by the Baeyer-Villiger oxidation of the 2-ethoxycarbonylmethyl-cyclohexanone. Then, homopolymer and copolymers were accomplished in bulk (130 degrees C) by ring-opening polymerization in the presence of stannous 2-ethyl hexanonate (Sn(Oct)(2) as catalyst. All the polymers were characterized by FTIR, H-1-NMR, C-13-NMR, GPC, and DSC. The melting temperature (T-m) decreased with an increase of ECL content because the molecular weight decreased in corresponding. It was also noted that Delta H-m for copolymers increased with an increase in the molecular weight because the relative number of copolymer chain ends and pendant functional groups decreased with a decrease of content of ECL. We think the availability of pendent groups on poly (epsilon-caprolactone) has great potential for applications in medicine, surgery, and tissue engineering.