Fast monomers: Factors affecting the inherent reactivity of acrylate monomers in photoinitiated acrylate polymerization

A systematic study on the effect of molecular structure on the photoinitiated polymerization of acrylates was undertaken. Initially, the research was focused on the effect of hydrogen bonding, and it was found that preorganization via hydrogen bonding enhances the maximum rate of polymerization (R-p). This hydrogen bonding facilitated preorganization also affected the tacticity of the resultant polymer. Next, the effect of polarity as represented by the calculated dipole moment (mu(calc)) of a given monomer was investigated. A direct linear correlation between R-p and the calculated Boltzmann-averaged dipole moment (mu(calc)) was observed. The R-p-mu(calc) correlation holds for pure monomers, mixtures of monomers, and even mixtures of monomers with inert solvents. This correlation enables the rational design of monomers with a required reactivity. In addition, these studies suggest that the propagation step of polymerization is influenced by hydrogen bonding while the dipole moment influences the termination rate constant. These two mechanistic explanations can be regarded as complementary factors that influence the speed of acrylate polymerization.