p-Bis(bromomethyl)benzene with silyl groups [SiMe3(2a), SiEt3(2b), SiMe2-t-Bu (2c), SiMe2-n-Bu (2d), SiMe2-n-C8H17 (2e), SiMe2-n-C18H37 (2f)] were polymerized by a modified Gilch route to afford silyl-substituted poly(p-phenylenevinylene)s (3a-f). The polymer containing SiMe3 groups (3a) was insoluble in any solvents, while the other polymers (3b-f) were soluble in organic solvents. They had relatively high molecular weight over 3.6 x 10(4), and gave free-standing membranes by solution casting method. According to thermogravimetric analysis (TGA), the silyl-substituted poly(p-phenylenevinylene)s showed high thermal stability (T-d >= 300 degrees C). The oxygen permeability coefficients of membranes of the silylsubstitu tedpoly(p-phenylenevinylene)s (3b-f) were in the range of 3.5-12 barrers, and the poly(p-phenylenevinylene)s with long alkyl silyl groups, 3e and 3f, exhibited the highest gas permeability among them. This is the first report on gas permeability of poly(p-phenylenevinylene)s. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 2009-2015, 2010