Molecular simulation of small molecule diffusion and solution in dense amorphous polysiloxanes and polyimides

Results of extensive molecular modeling investigations on the transport of different small molecules in flexible chain rubbery polysiloxanes and stiff chain glassy polyimides are discussed. Extended equilibration procedures w ere necessary to obtain reasonable packing models for the polyimides. The t ransition state Gusev-Suter Monte Carlo method was utilised to prove a reas onable coincidence between simulated and measured diffusivity and solubilit y values for the model structures. A comparison between the static structur e and the dynamic behaviour of the free volume in the simulated flexible ch ain rubbery polymers and stiff chain glassy polymers reveals qualitative di fferences which are decisive for experimentally observable differences in t he diffusion of small molecules in these materials. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.