Relationship between composite matrix molecular structure and properties.

The synthesis of three novel dimethacrylate esters for use as the monomer phase in dental composites was studied. The monomers were prepared by the reaction of glycidyl methacrylate with phthalic, isophthalic and terephthalic acids, respectively, and the reaction products were found to be mixtures of isomers. The monomers obtained from the reaction of phthalic and isophthalic acids were low-viscosity liquids and the relationship between viscosity and molecular structure was studied. The low viscosity of these di-hydroxyl containing monomers was shown to be due to intramolecular hydrogen bonding. This reduced monomer viscosity compared with BisGMA allowed a reduction in the quantity of diluent monomer triethyleneglycoldimethacrylate (TEGDMA) required to give standard viscosities of 1 and 2 Pas resulting in a modest decrease (ca. 10%) in polymerization shrinkage compared with that exhibited by BisGMA/TEGDMA solutions of equivalent viscosities. A number of properties relevant to the use of these as potential core monomers in dental composites were determined for both monomer and polymer systems.