The bonded constants in the DREIDING force field have been parameterized for poly[1-( trimethylsilyl)-1-propyne] (PTMSP) from AMI calculations of the dimer. The resultant force field has been validated through the simulation of amorphous cell density and x-ray data (d-spacing) and used to obtain diffusion coefficients for five gases (He, O-2, N-2, CH4, and CO2) from 0.5 ns NVT molecular dynamics using the Einstein relationship. In addition, solubility coefficients of these gases have been obtained from the particle insertion method of Bezus et al. and from a fixed-pressure Monte Carlo method which was also used to calculate sorption isotherms. In general, there is good to excellent agreement between experimental and simulated values of the diffusion and solubility coefficients for He, O-2, N-2, and CH4. Sorption isotherms and dual-mode parameters calculated from the simulation results for O-2, N-2, and CH4 agree very favorably with experimental data (no experimental data was available for He). In the case of CO2, diffusion and solubility coefficients as well as sorption isotherms are underestimated. The less satisfactory results for CO2 have been tentatively attributed to inadequacy of the generic nonbonded Lennard-Jones potential terms of DREIDING used in this study.