Metathesis polymerization of disubstituted acetylenes

The structure of the monomer can be a crucial factor with these catalysts. Thus MeC=CBu is polymerized by both MoCls/PluSn and WCl6/Ph4Sn in toluene at 30°C (Higashimura 1982), but the more sterically hindered MeC=CCHMc2 is polymerized only by WCVPluSn at 60°C (Masuda 1982a). 

The relative proportions of linear polymer and cyclic trimers produced from disubstituted acetylenes are dependent on the catalyst system and are therefore 

Certain metal alkyne complexes are capable of initiating the polymerization of dialkylacetylenes, no doubt first being converted into metal carbene complexes. For complexes of the type Mo(=CCMe3)(OR)3 the nature of OR is critical for a substrate such as EtC=CPr. If OR is OCMe3, there is no reaction if OR is OCMe(CF3)2, the acetylene is metathesized only if OR is OCHMe2 or OCH2CMe3 does the acetylene polymerize (McCullough 1984, 1985). 

Polymers of other unsymmetrical disubstituted acetylenes, such as MeC=CPr, have somewhat broad NMR signals, and may well contain HH and TT as well as HT structures (Higashimura 1982). These polymers are generally white and have intrinsic viscosities which are sometimes nearly proportional to the MW, for example, the polymer of EtC=CPh (Masuda 1985c). This indicates that the polymer molecules have a fairly rigid but twisted backbone with very little 

Further details, including the physical properties of polyacetylenes, may be found in the reviews of Masuda (1987d, 1994b) and Breslow (1993). 

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Table 10.4 References to the metathesis polymerization of disubstituted acetylenes"... 

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