Synthesis, characterization, and enzymatic degradation of copolymers prepared from ε-caprolactone and β-butyrolactone

A series of copolymers was prepared by ring-opening polymerization of E-caprolactone and (R,S)-beta-butyrolactone using zinc lactate as catalyst. The resulting PCL/PBL copolymers were characterized by various analytical techniques such as NMR, SEC, DSC, and X-ray diffraction. The CL/BL ratio was higher in the copolymers than in the feeds, indicating a higher reactivity of E-caprolactone with respect to beta-butyrolactone. The copolymers appeared to be semicrystalline, the crystalline structure being of the PCL-type. Compression-molded polymer films were allowed to degrade in a pH = 7.0 phosphate buffer containing Pseudomonas lipase. Data showed that the copolymers degraded faster than the PCL homopolymer. Various soluble degradation products were detected in the degradation medium. ESEM micrographs confirmed the enzymatic degradation occurred by surface erosion.