Synthesis and characterization of functionalizable and photopatternable poly(ε-caprolactone-co-RS-β-malic acid)

To create a functionalizable and photopatternable biodegradable polyester, 2-hydroylethyl methacrylate (HEMA) grafted poly(ε-caprolactone-co-RS- β-malic acid) (PCLMAc) was synthesized. The ring-opening random copolymerization of ε-caprolactone (CL) and RS-β-benzyl malolactonate (MA) using stannous octoate catalyst was systemically studied. The polymers were characterized by ¹H NMR, FTIR, GPC, and DSC. The optimum copolymerization temperature was found to be 130°C. The proportion of MA in the derived copolymers was lower than that in the feeding dose, a consequence of its lower reactivity. The molecular weight of the copolymers decreased with increasing MA content. During hydrogenolysis, the protective benzyl groups were completely replaced by carboxyl groups resulting in hydrogen bonding in the deprotected copolymers, but some degradation occurred. PCL segments in the copolymers crystallized when the MA content was lower than 16.2 mol %, and the deprotected copolymer had higher crystallinity compared to that of the corresponding protected copolymer. The glass transition temperature (T _g) of the deprotected copolymer increased greatly due to the formation of hydrogen bonds. HEMA was easily grafted on the functionalized biodegradable copolymer. The liquid HEMA grafted copolymer was shown to be suitable for UV microembossing.