Functionalized multiarm poly(ϵ‐caprolactone)s: Synthesis, structure analysis, and network formation

The purpose of this research was to synthesize and characterize a novel class of four‐arm, star‐shape biodegradable polymers having double‐bond functionality as a precursor for free‐radical polymerization, with unsaturated monomers or macromers or photocrosslinking for network formation. The synthesis involved two basic steps. First, hydroxyl‐functionalized four‐arm poly(ϵ‐caprolactone)s (PPCL‐OH) were synthesized by the ring‐opening polymerization of ϵ‐caprolactone in the presence of pentaerythritol and stannous octoate. Second, double‐bond–functionalized four‐arm poly(ϵ‐caprolactone)s (PPCL‐Ma) were synthesized by reacting PPCL‐OH with maleic anhydride in the melt at 130°C. Quantitative conversion of hydroxyl functionality in PPCL‐OH to double‐bond functionality was achieved for low molecular weight PPCL‐OH. Both the PPCL‐OH and the PPCL‐Ma were characterized by FTIR, 1H‐NMR, 13C‐NMR, SEC, and DSC. The capability of the double‐bond–functionalized four‐arm poly(ϵ‐caprolactone)s (PPCL‐Ma) to form network structures was preliminarily shown by photocrosslinking PPCL‐Ma.