Analytical and preparative polymethacrylate monolith fabrication: effect of porogen content and column size on pore morphology

Abstract

Contrary to previous studies that focused only on ≤ 5-cm internal diameter (id) monolith, this paper describes the pore morphology of porous polymethacrylate monolithic adsorbents produced via bulk free radical polymerization in small, medium, and large-scale columns (specifically, columns with id of 1.5, 5, 8, and 17 cm). Different radial sections of the monoliths were studied under the scanning electron microscope, and the pore size was estimated using ImageJ software. Parameters such as exotherm and thermal stability during polymerization were analyzed. In this experiment, the effects of porogen contents on the pore morphology were relatively similar throughout all the monolith sizes, whereas the degree of exotherm and the heterogeneity were directly proportional to monomer/porogen ratio. An increase in monolith diameter/volume hampered the internal heat dissipation, resulting in rupture of the adsorbent structure. Results from this study show that the intensity of thermal buildup and column id are non-linearly correlated with both 8.0 and 17.0-cm id monoliths recording similar T max values. Furthermore, the effect of heat buildup on the porosity of monolith was found to be negligible. In summary, these polymerization parameters (porogen content, column id, and reaction temperature) could be used to predict the maximum exothermic heat released hence maximum temperature buildup during the fabrication of large-scale monoliths.