Diffusion (D) and permeability (P) coefficients of poly(3,4-bis(trimethylsiloxy)silylItricyclononene-7) (PTSOTN), a metathesis ring opening polymer with Si-O-Si containing side groups, were measured for light gases (He, H-2, O-2, N-2, CO2) and hydrocarbon C-1-C-4. For the hydrocarbons C-2-C-4 the measurement was conducted in the pressure range of 0-2 atm. Using a novel technique, sorption isotherms in this polymer were obtained for all the aforementioned penetrants in the range of 0-2.5 atm, It was shown that the slope of the correlation of In D versus d(2) for PTSOTN is intermediate between those characteristic for polymers with solubility controlled selectivity and size sieving glassy polymers. A comparison of the permselectivity alpha, diffusion selectivity alpha(D) and sorption selectivity alpha(S) indicated that the solubility controlled permeation in PTSOTN is caused by the reduced diffusivity selectivity of this polymer. (C) 2015 Elsevier B.V. All rights reserved