Modeling of low-temperature depolymerization of poly (methyl methacrylate)promoted by ion beam

The role played by the ion beam in the depolymerization of poly(methyl meth acrylate) (PMMA) is the creation of initiators for the unzipping reaction a t relatively low temperatures [lower than the ceiling temperature of PMMA ( T-C=220 degrees C)]. Monomer (MMA) evolution out of the polymeric film is t hus governed by the kinetics of the chemical reaction and also by the diffu sion of monomer inside the polymeric film. In this work this phenomenon has been described by using simple models in which both one- and two-dimension monomer diffusion is considered. Exact analytical solutions of the models are provided. The theory fit well the experimental data and allows for the determination of important parameters such as the kinetics constant of the depolymerization and the monomer diffusion coefficient, D, inside the polym er film. Thus, the pulsed ion beam technique, here modeled, is useful not o nly for extracting D values of slow diffusants in polymers, but even for me asuring kinetics constants of depolymerization at a temperature well below that needed for the formation of suitable thermal initiators. (C) 1999 Amer ican Institute of Physics. [S0021-9606(99)50727-7].