MALDI-TOF analysis of the secondary processes occurring during the ring opening polymerization of caprolactone initiated by HEMA

Short 2-hydroxyethylmethacrylate (HEMA)-oligocaprolactone macromonomers were synthesized at different temperatures from 100 degrees to 190 degrees C by bulk ring opening polymerization using HEMA as initiator and stannous octoate as catalyst. The crude products were analysed by MALDI-TOF and NMR and the influence of the temperature on the reaction was studied. In addition to transesterification (found at temperatures of 130 degrees C and higher), other secondary reactions involving HEMA breakdown were also identified at these temperatures. In these processes, difunctional acrylic compounds may be formed.