Three disubstituted acetylenes with an adamantyl group-1-(p-adamantylphenyl)-2-chloroacetylene (ClpAdPA), 1-(p-adamantylphenyl)-1-propyne (pAdPP), and 1-(p-adamantylphenyl)-2-phenylacetylene (pAdDPA)-polymerized in good yields in the presence of MoCl5- or TaCl5-based catalysts. The highest weight-average molecular weights of poly(ClpAdPA), poly(pAdPP), and poly(pAdDPA) reached 3.6 x 10(5), 1.1 x 10(6), and 6.0 x 106, respectively. The polymers were yellow to white solids and completely soluble in toluene, chloroform, and so forth. These polymers thermally were fairly stable, and the onset temperatures of weight loss in air were over 360 degrees C. Poly(pAdPP) and poly(pAdDPA) provided free-standing films by solution casting, and their oxygen permeability coefficients (P-O2) at 25 degrees C were 8.6 and 55 barrers [1 barrer = 1 x 10(-10) cm(3).(STP).cm/(cm(2).s.cm Hg)], respectively, which are relatively small compared to those of other substituted polyacetylenes.