Kinetic study of alkyl methacrylate polymerization in nanoporous confinement over a broad temperature range

The effect of nanoconfinement on the free radical polymerization of ethyl methacrylate (EMA) and n-butyl-methacrylate (BMA) with di-tert-butyl peroxide (DtBP) initiator is investigated over a wide temperature range from 80 to 190 degrees C using differential scanning calorimetry. The effective rates are similar for the two bulk monomers although the BMA reacts approximately 11% faster at 95 degrees C. For nanoconfined cases, the initial reaction rate for monomer confined in the pores of controlled pore glass is enhanced, with larger effects observed in native pores compared to pores in which the native silanol was converted to trimethyl silyl. The onset of autoacceleration also occurs earlier under nanoconfinement, with decreases in both the conversion and the time required to reach autoacceleration, x(gel) and t(gel), respectively, and larger changes for the native pores. The induction time follows Arrhenius behavior and increases under nanoconfinement. At polymerization temperatures above 160 degrees C, depropagation becomes important as the ceiling temperature is approached and seems to be more pronounced under nanoconfinement than in the bulk.