Monte Carlo simulation of density dependence of molecular motion and radical decay in solid polymers

It was found experimentally that after increasing pressure, the decay of free-radicals in solid polymers is slowed down (Szöcs F, Rostašová O, Tiňo J, Plac̆ek J, European Polym J, 1974;10:725). Since the mechanism for decay is associated with molecular mobility, a Monte Carlo method has been used for studying the effect of the polymer density on molecular mobility and free-radical decay in a model system with the parameters close to those of polyethylene. Increased pressure is correlated with higher density of the polymer system. Rotational motions were found to be considerably limited at increased density (ρ=0.85 g cm⁻³ versus 0.81 g cm⁻³). Consequently, free-radical decay is slowed down at the higher density in accord with the experimental results.