The system composed of water, sodium dodecyl sulfate, methyl methacrylate, and 2-hydroxyethyl methacrylate, with and without ethylene glycol dimethacrylate as a cross-linking agent was used to investigate the effects of changing from visible-light to thermal polymerization. Thermal polymerization yielded porous solids within the range 20−80 wt % aqueous phase content for systems with and without cross-linker. Microstructures similar to photoinitiated polymers were observed in all ranges analyzed. Closed cell microstructures were found to exist for polymers with aqueous fractions less than 50 wt % for polymers with and without cross-linker. Polymers with aqueous fractions greater than or equal to 50 wt % were found to exhibit an open cell microstructure. These microstructures for the higher aqueous fractions differed from the previously observed morphology in other microemulsion systems. These polymers were found to be porous with polymer droplets interconnected to produce a solid mass. Also, a flakelike appearance was found in certain compositions. Both of these occurrences were also recorded for a previous photoinitiated study. The level of cross-linker was found to have a negligible effect on the maximum pore sizes observed, although cross-linker did cause a general shifting of polymers toward closed cell microstructure.