POLYMERIZATION OF HETEROATOM CONTAINING ACETYLENES .6. POLYMERIZATION OF 1-(TRIMETHYLSILYL)-1-PROPYNE HOMOLOGS CONTAINING 2 SILICON ATOMS BY TANTALUM-BASED AND NIOBIUM-BASED CATALYSTS

Polymerization of new 1-(trimethylsilyl)-1-propyne homologs containing two silicon atoms left bracket CH//3C EQUVLNT CSi(CH//3)//2CH//2Si(CH//3)//3 and CH//3C EQUVLNT CSi(CH//3)//2CH//2CH//2Si(CH//3)//3 right bracket was investigated by use of Ta and Nb catalysts. CH//3C EQUVLNT CSi(CH//3)//2CH//2Si(CH//3)//3 was polymerized quantitatively by TaCl//5 alone to provide a polymer having molecular weight over 10**6. CH//3C EQUVLNT CSi(CH//3)//2CH//2CH//2Si(CH//3)//3 was polymerized in good yield by an equimolar mixture of TaCl//5 with an appropriate organometallic cocatalyst such as Ph//4Sn to give a polymer with molecular weight of ca. 4 multiplied by 10**5. Nb catalysts were less active toward these monomers than the corresponding Ta catalysts. These two kinds of polymers had alternating double bonds along the main chain according to IR and **1**3C-NMR spectra. Both polymers were white solids completely soluble in low-polarity solvents like toluene, and solution casting afforded uniform, tough films.