Hydrogen bonding and rate enhancement in the photoinduced polymerization of telechelic urethane methacrylates based on a cycloaliphatic system: Tricyclodecane dimethanol

Abstract

AbstractA new class of telechelic urethane methacrylic crosslinkers, based on a cycloaliphatic system (tricyclodecane dimethanol and tricyclodecane monomethanol), was synthesized. The synthesis was achieved by a two‐step condensation of 1,6‐hexamethylene diisocyanate or isophorone diisocyanate with tricyclodecane dimethanol and capping with hydroxyethyl methacrylate. Samples of hexanediol diacrylate, tricyclodecane monomethacrylate, and tricyclodecane dimethacrylate were used as non‐hydrogen‐bonding monomers for comparative studies of the curing kinetics. The photopolymerization of these telechelic systems was investigated with UV irradiation in the presence of 2,2‐diethoxy acetophenone as the photoinitiator, and the kinetics were followed by the monitoring of the double‐bond conversion at 815 cm−1 with Fourier transform infrared spectroscopy. The hydrogen‐bonded crosslinkers had higher double‐bond conversions than their non‐hydrogen‐bonded counterparts under identical conditions. The higher cure rate could be explained by hydrogen‐bonding preassociation in these systems, which brought the methacrylate double bonds within close proximity. The temperature effects on the hydrogen bonding were also investigated. A decrease in the extent of the double‐bond conversion with increasing temperature was observed for the hydrogen‐bonded crosslinker, in contrast to an increased conversion with temperature for hexanediol diacrylate and tricyclodecane dimethacrylate. This was directly indicative of a reduction of hydrogen bonding at elevated temperatures leading to lower conversions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4384–4395, 2006