(o-Alkylphenyl)acetylenes (alkyl: Et, n-Bu, n-C6H13, n-C8H17, and iso-
Pr) polymerized in high yields with W and Mo catalysts. MoCl5-based ca
talysts, which are not very active to phenylacetylene (PA), exhibited
high activity like the WCl6 counterparts. The weight-average molecular
weights (M(w)BAR) of the polymers having o-n-alkyl groups were in the
range 2 x 10(4)-55 x 10(4), being similar to or slightly higher than
those of poly(PA), while the highest M(w)BAR value of poly(o-iso-Pr-ph
enylacetylene) [poly(iso-PrPA)] reached 1 x 10(6). The formed polymers
were dark red, and had the structure [CH = C(C6H4-alkyl)]n. They were
thermally more stable than poly(PA) according to the thermogravimetri
c analysis. The polymers with long o-n-alkyl groups were soluble in al
iphatic solvents (e.g., hexane) unlike poly(PA), and their softening p
oints were lower. Poly(o-iso-PrPA) was film-forming, and fairly gas-pe
rmeable (P(O2) 27 barrers, P(O2)/P(N2) 2.2).