The cross-linking reaction of 15 dimethacrylates, one trimethacrylate and five diacrylates was studied by means of differential scanning calorimetry (DSC) and high performance liquid chromatography (HPLC) to investigate the relationship between the polymerization characteristics and the chemical structure of these monomers.
The amount of pendant double bonds (Dp) and the efficiency of cross-linking (Ec) were calculated from both the extent of polymerization (Ep) and the amount of residual monomer (Rm) obtained by DSC and HPLC analyses, respectively. The Ep and Ec values of various monomers increased with an increase in the number of chain members between the functional groups, while Rm and Dp values decreased.
The dimethacrylates consisting of aliphatic chains polymerized more readily than those containing aromatic units. High Ep was obtained in the aliphatic dimethacrylates and diacrylates with more than eight chain members and the aromatic dimethacrylates with more than 20 chain members among the monomers examined. These results depend presumably on the flexibility of the functional groups in the polymer network. With most dimethacrylates and diacrylates, high Ep was also observed in thermal scanning polymerization compared to isothermal polymerization at 90ยฐC. The diacrylates showed a high rate of polymerization compared to the corresponding dimethacrylates.