PREPARATION OF LARGE-DIAMETER MOLDED POROUS POLYMER MONOLITHS AND THECONTROL OF PORE STRUCTURE HOMOGENEITY

The preparation of large cylindrical macroporous polymer monoliths wit h internal diameters of up to 50 mm has been studied for the first tim e for both styrenic and methacrylic monomer systems. The temperature p rofiles at different locations within the mold have been recorded duri ng these polymerizations, and the occurrence of exotherms and temperat ure gradients was related to the creation of inhomogeneities in tile p ore structure, Several techniques, such as decreasing the rate of poly merization and a slow gradual addition of the polymerization mixture t o the reaction vessel, were investigated in order to minimize the exte nt of the reaction exotherm. The latter approach proved especially pow erful, as the absence of exotherm allowed the preparation of monoliths with homogeneous pore structures inaccessible by other methods for bo th monomer systems.