(16d) Development Of Quantitative Structure-Property Relations For Crosslinked Polymethacrylate Resins For Dental Applications

Novel dental materials with improved physical and chemical properties are in great demand, as current polymeric resins are subject to attack by water and salivary esterases. Crosslinked, photocurable polymethacrylate polymers are often used in dental restoration applications, and are the focus of this research. New polymers can be designed by optimizing their chemical structure based on an objective function derived from quantitative structure-property relations (QSPRs). Glass transition temperature, tensile strength, and esterase resistance are used in the initial polymer screening. The goal of this work is to create QSPRs for critical properties of polymethacrylates and related materials, for use within a computational molecular design methodology to develop novel adhesive resins for dental restoration applications. Many physical and chemical properties of linear polymers can be estimated from the chemical structure of their repeat units by correlations based on group contributions or topological descriptors. In addition to the chemical structure of the repeat unit, the degree of polymerization, the crosslink density, and heterogeneous structures affect polymethacrylate properties. Current property estimation methods generally do not account for crosslinking and are, therefore, not applicable to dental resins used in restorative materials. The crosslink density and the degree of polymerization are readily measured experimentally, but are difficult to estimate for polymers which have not been synthesized. Crosslinking in this case is accomplished by using monomers with additional methacrylate groups. An estimate of crosslinking can be obtained by looking at the number of sites available for crosslinking, but complete conversion is rarely achieved. In this research, the limiting conversion is used to avoid the need to consider kinetic effects. Descriptors related to steric effects and intermolecular forces are employed along with statistical analysis of experimental data to predict crosslinking and conversion for new polymers. The experimental data used comes from studies on polymethacrylate produced using the same methods, to provide a consistent data set. QSPRs for important properties which take into account crosslink density are generated through statistical analysis of experimental data. A methodology is presented which allows for rapid estimation of physical and chemical properties of crosslinked polymers. The method is suitable for use within optimization algorithms for designing novel polymers for dental applications.