Abstract: The formation of membranes from copolymer of trimethylsilyl propyne with pentamethy-ldisilyl propyne poly(TMSP-co-PMDSP) has been investigated. The copolymer exhibited asimilar performance in membrane formation and gas permeability as the homopolymer PTMSP.Its permeability coefficients and separation factors were P_O2 = 4×10³～12×10³, P_N2 = 3×10³～8×10³, P_CO2 = 2×10⁴～4×10⁴ Barrer and α_O2/N2 = 1. 3～1. 9, respectively. The gas permeationbehaviour was dependent on the thickness of the membrane and deviated from the SecondFick law. In the presence of organic condensed gas, the gas permeability appeared to becontrolled by surface adsorption of gas. The gas permeability coefficient decreases withthe increase of the storage time and temperature because the solubility coefficient reductionΔS of the membrane was greater than its diffusibility coefficient increase ΔD. The gas per-meability was deeply influenced by the thermal history of the membrane.

Key words: trimethylsilypropyne, pentamethyldisilyl propyne, copolymer, membrane, gas permeability