Kinetic model of a methacrylate-based monolith polymerization

Monolithic stationary phases are becoming more and more important in the fi eld of liquid chromatography, because they enable extremely fast separation s. Methacrylate-based monoliths are produced via a free-radical bulk polyme rization of glycidyl methacrylate and ethylene dimethacrylate using a benzo yl peroxide as an initiator. Preparation of large monoliths represents a bi g problem because of the heat release during the polymerization, which cons equently leads to the distortion of the structure. A closer investigation o f the polymerization, using differential scanning calorimetry, was performe d in order to determine global kinetic parameters. A multiple heating rate method, based on the work of Ozawa, Flynn, and Wall, was applied for estima tion of the values of the apparent activation energy, preexponential factor , and reaction order. Global polymerization kinetics is of first order with A = 1.681 x 10(9) s(-1) and E-a,E-app = 81.5 kJ/mol, where the heat of pol ymerization is approximately 190 J/g. In addition, the influence of air and nitrogen atmosphere on polymerization is presented.