Thermodynamic and Kinetic Considerations - Effect of Organic Siloxane on MMA Polymerization

Abstract

The effects of 3-(methacryloxypropyl)-trimethoxysilane (MATS) and vinyl trimethoxysilane (VTMOS) on methyl methacrylate (MMA) polymerization have been investigated. The two co-monomers appear to show opposite effects. The polymerization shows a higher rate of polymerization and extent of conversion in the presence of MATS than in its absence. However, a lower rate of polymerization and extent of conversion are obtained in the presence of VTMOS. The difference can be related to the different roles of the co-monomers. The increase in the rate of polymerization and conversion with MATS can be attributed to the higher reactivity of monomers. The lower conversion with VTMOS may be due to the electronic effects associated with VTMOS, which can decrease the electric density of the active double bond in MMA and therefore deactivate the polymerization. Further investigation shows that the change of free energy in the polymerization with MATS is lower than without MATS. Also, monomer reactivity in the presence of MATS is higher than in the absence of MATS. The decrease in free energy may be a thermodynamic response to the increase in the conversion. The increase in monomer reactivity may be responsible for increasing the rate of polymerization.