The reaction kinetics during bulk free radical polymerization is still not fully understood. As the reaction proceeds, many parameters, including monomer/polymer fraction, radical concentration, viscosity, and temperature, change in a nonequilibrium manner. In this study, we investigate the bulk polymerization of methyl methacrylate, focusing on a sudden acceleration in reaction kinetics known as the Trommsdorff effect. Dielectric spectroscopy shows that a temperature increase occurs at the vicinity of polymerization-induced vitrification. At the same timing as the temperature increase, the polymerization solution becomes heterogeneous. This heterogenization causes a decrease in transmittance at a wavelength of 400 nm. We discuss phenomena related to the Trommsdorff effect, including the kinetic heterogenization, vitrification, change in the amorphous structure, and the formation of discontinuously high-molecular-weight polymers.

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It has been demonstrated that nano- or micro-structured polymeric materials have huge potential as advanced materials. However, most of the current fabricating methods have limitations either in cost or in size. Here, we investigate the bulk polymerization of methyl methacrylate in the presence of poly(ethylene glycol) (PEG). We found that phase separation occurs during bulk polymerization. After removal of PEG via sonication, microscopic structures of poly(methyl methacrylate), including porous structures, co-continuous monolith structures, or particle aggregation structures, are formed. These structures can be controlled by the amount of PEG added and the reaction temperature. The results are summarized in phase diagrams. The addition of PEG significantly affects the reaction kinetics. Phase separation is coupled with the reaction acceleration known as the Trommsdorff effect. As a result, the reaction completes in a shorter time when the PEG amount is higher. We demonstrate surface coating to fabricate an amphiphobic surface, repelling both water and oil. The methods presented here have the potential to fabricate microscopic structures in large areas cost-effectively.

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