Preparation of Large-Diameter "Molded" Porous Polymer Monoliths and the Control of Pore Structure Homogeneity

The preparation of large cylindrical macroporous polymer monoliths with internal diameters of up to 50 mm has been studied for the first time for both styrenic and methacrylic monomer systems. The temperature profiles at different locations within the mold have been recorded during these polymerizations, and the occurrence of exotherms and temperature gradients was related to the creation of inhomogeneities in the pore structure. Several techniques, such as decreasing the rate of polymerization and a slow gradual addition of the polymerization mixture to the reaction vessel, were investigated in order to minimize the extent of the reaction exotherm. The latter approach proved especially powerful, as the absence of exotherm allowed the preparation of monoliths with homogeneous pore structures inaccessible by other methods for both monomer systems.