The polymerization of a novel monomer p-(t-butyldimethylsiloxy)tolan (1) with TaCl5-n-Bu4Sn provided a high molecular weight polymer (poly(1)), whose M-w reached 4.0 X 10(6). The poly(1) membrane was prepared by the casting method, and converted into poly[(p-hydroxy)tolan] (poly(2)) with a mixture of trifluoroacetic acid/water. Whereas poly(1) dissolved in low polarity solvents such as toluene and chloroform, poly(2) was practically insoluble in any solvents, although it partly dissolved in methanol and ethanol. The onset weight loss temperatures of poly(1) and poly(2) in air were 320 and 360degreesC, respectively, indicating fair thermal stability among substituted polyacetylenes. The oxygen permeability coefficients (P-O2) of poly(1) was 150 barrers, which is relatively small among polytolan derivatives, while that of poly(2) was 8.0 barrers and smaller owing to the presence of polar hydroxyl groups. (C) 2004 Elsevier Ltd. All rights reserved.