High-permeance collection layers are needed in composite membranes but few polymers have the required permeability. Hydrosilylation condensation polymers, because of their high silicon content, were thought to be good candidates to have high permeabilities. Several novel polymers were made and a new and simpler synthesis of ethynylated silanes is reported. One polymer, poly(divinyldimethylsilane-co-1,4-bis[dimethylsilyl]benzene), appears to be of a liquid crystalline nature and has a low oxygen permeability (1.10 barrers). Two others [poly(diethynyldimethylsilane-co-1,4-bis[dimethylsilyl]benzene and poly (divinyldimethylsilane- co-p,p’diethynylbiphenyl-co-tetramethyldisiloxane) ] were viscous liquids that could be thermally cured to give elastomers with oxygen permeabilities of approximately 85 barrers.