[o‐(Trimethylgermyl)phenyl]acetylene was polymerized in the presence of WCl6, W(CO)6‐hv, etc., to give polymers whose weight‐average molecular weights reached ca. 7.0 X 105 at the highest. When the MoOCl4‐n‐Bu4Sn‐EtOH (1 : 1 : 1) catalyst was used, the polydispersity ratio of the polymer obtained was 1.08, and the number‐average molecular weight increased in direct proportion to monomer conversion; these indicate that this polymerization is a living polymerization. The polymer had the structure  [CHC(C6H4‐o‐GeMe3)]n  and was a dark purple solid (λmax = 551 nm, εmax = 6100 M‐1 cm‐1 in THF) soluble in organic solvents such as toluene and chloroform. The onset temperature of weight loss of the polymer in TGA in air was ca. 230°C, and the glass transition temperature was above 180°C. The Po2 of the present polymer is 105 barrers—larger than the value of natural rubber and fairly close to that of poly(dimethylsiloxane). © 1993 John Wiley & Sons, Inc.

Polymerization of phenylacetylenes (PAS) having various ortho-substituents were examined by using MoOCI,-n-Bu,Sn-EtOH (mole ratio 1 : 1 : 1) as catalyst. Phenylacetylenes with no or sterically small ortho-substituents did not polymerize in a living fashion. On the other hand, in the polymerization of phenylacetylenes having medium-sized substituents (e. g., CH,, C1, Br, and iPr), the number-average molecular weights M, of polymers increased in direct proportion to monomer consumption, while the polydispersity ratios were 1,2-1,3, which is in favor of living polymerization. Further, monomers having bulky ortho-groups (CF, and Me,Ge) exhibited excellent living nature with small polydispersity ratios of = 1 , l . Thus, it is concluded that not the electronic but the steric effect of the ortho-substituent is important to achieve living polymerization.

ABSTRACT:(o-Alkylphenyl)acetylenes (alkyl: Et, n-Bu, n-C6 H 13 , n-C8 H 17 , and iso-Pr) polymerized in high yields with W and Mo catalysts. MoCl 5 -based catalysts, which are not very active to phenylacetylene (PA), exhibited high activity like the WCl6 counterparts. The weight-average molecular weights (Mw) of the polymers having o-n-alkyl groups were in the range 2 x 10 4 -55 x 104, being similar to or slightly higher than those of poly(PA), while the highest Mw value of poly(o-iso-Pr-phenylacetylene) [poly(iso-PrPA)] reached I x 10 6 • The formed polymers were dark red, and had the structure --fCH=C(C6 H4 -alkyl)k They were thermally more stable than poly(PA) according to the thermogravimetric analysis. The polymers with long o-n-alkyl groups were soluble in aliphatic solvents (e.g., hexane) unlike poly(PA), and their softening points were lower. Poly(o-iso-PrPA) was film-forming, and fairly gas-permeable (P02 27 barrers, P0 ,/PN, 2.2).KEY WORDS Substituted Acetylene/ ( o-Alkylphenyl)acetylene / TransitionMetal Catalyst / Metathesis Polymerization / Substituted Polyacetylene / Gas Permeability / In the polymerization of monosubstituted acetylenes by W and Mo catalysts, a general tendency has been observed that monomers with bulky substituents provide high molecular weight polymers. For instance, 1-hexyne, which is sterically not crowded, forms only oligomers whose weight-average molecular weights (M w) are a few thousand. 1 • 2 In contrast, tertbutylacetylene, which is very crowded, produces a polymer whose Mw exceeds 1 x 10 5 . t -4 The steric effect of phenylacetylene is moderate, and the M w of the polymer formed is usually 2 X 10 4 -3 X 10 4 . 1 • 5 W(C0) 6 -hv catalyst) and good thermal stability. 6 It has recently been found that phenylacetylenes with even bulkier ortho groups (e.g., CF 3 7 and Me 3 Si 8 • 9 ) yield polymers with very high molecular weight (Mw 1 x 10 6 and above).Thus it is interesting to examine how high the molecular weight of the polymer becomes when a substituent is introduced onto the ortho position of phenylacetylene to increase steric crowding. In fact, we studied the polymerization of(o-methylphenyl)acetylene (o-MePA) to find the formation of a polymer having high molecular weight (Mw up to 8 x 10 5 with * To whom correspondence should be addressed.The present study deals with the polymerization of (o-alkylphenyl)acetylenes, namely, phenylacetylenes having ethyl, n-butyl, n-hexyl, n-octyl, and iso-propyl groups at the ortho position

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