Abstract: Diarylacetylene monomers(1a~1d) containing substituted biphenyl and Si groups were synthesized and then polymerized with TaCl₅-n-Bu₄Sn catalyst to generate the corresponding polymers(2a,2b,and 2d).The produced polymers showed good solubility in common organic solvents.Polymers 2a and 2b afforded free standing membranes by casting from their toluene solution.Desilylation of membranes 2a and 2b was carried out with trifluoroacetic acid to give membranes 3a and 3b,which were insoluble in any organic solvents.According to thermogravimetric analysis,both the trimethylsilyl-containing and the desilylated polymers exhibited high thermal stability,the onset temperatures of mass loss in air were 340℃ and 430℃,respectively.The oxygen permeability coefficients(P_O2) of polymers 2a and 2b were 99 and 160 barrers,respectively.Upon desilylation,the P_O2 of 3a and 3b decreased to 22 and 65 barrers,respectively.The separation factors of oxygen against nitrogen(P_O2/P_N2) of the present polymer membranes ranged from 2.4~3.3,and they tend to decrease as the P_O2 increased.By determining the gas diffusion coefficient(D) and gas solubility coefficient(S),the result indicates that the decrease of gas permeability upon desilylation was mainly derived from the decrease of D value.