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t-Butylacetylene was polymerized by MoC1 5 and WC16 as catalysts at 30oC or ooc in hydrocarbon and halogenated hydrocarbon solvents. Poly(t-butylacetylene) was obtained in high yield especially with MoC1 5 , and the highest polymer molecular weight exceeded 3 x 10 5 . The following relationship was obtained between the viscosity and molecular weight: [IJ]=I0-5 · 12 M/.Dl. The polymer was soluble in nonpolar solvents, particularly in aliphatic hydrocarbons. The infrared (IR), 1 H nuclear magnetic resonance (NMR), and 13 C NMR spectra supported the expected polymer structure, fCH=C(t-BuHn· A pair of doublets were observed for the methyl carbon in the 13 C NMR of polymer, making possible an evaluation of geometric structure.

Living polymerization of isobutyl vinyl ether (IBVE) was achieved with an equimolar mixture of hydrogen iodide (HI) and iodine in n-hexane at -15 eC to give nearly monodisperse poly (IBVE). The number-average molecular weight (Af") of the polymers increased in direct proportion to monomer conversion and to the reciprocal of the initial HI concentration. Their molecular weight distribution (MWD) remained nearly monodisperse (Mw/Mb 5 1.1) throughout the reaction. The polymerizations in other solvents (CH2C12 and toluene), in contrast, were not living and yielded polymers having broader MWD (Afw/Mn = 1.4-2.0), the Mn of which did not increase with conversion. Iodine ¿one could not effect a truly living IBVE polymerization in n-hexane; the Af" of the product polymers increased only slightly with conversion. The polymerization by HI alone in n-hexane was much slower than that by the HI/I2 initiating system. Interestingly, addition of iodine to a quiescent mixture of HI and IBVE led to a rapid polymerization that yielded nearly monodisperse polymers.

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The coefficients of permeability, diffusion and solubility (P, D and S, respectively) of various substituted polyacetylenes for six gases (He, H 2, 02, N2, CO2 and CH4) at 25°C were determined. The polyacetylenes with a bulky substituent such as poly[1-(trimethylsilyl)-l-propyne] (POly(TMSP)) generally exhibited large P values. The especially large P values (~2 x 10a-2 x 104 barrer) of poly(TMSP) were found to be based on both its D and S values being large. The polyacetylenes with a long n-alkyl group showed fairly large D values, while those with a phenyl group had relatively large S values. The activation parameters for P, D and S (Ep, E D and AHs, respectively) were obtained from their temperature dependences (30-70°C). The Ep values of poly(TMSP) were all negative (-9.7 to -0.4 kJ mol-1). This stemmed from its small E o values compared with those of other polymers.

Cationic polymerization of isobutyl vinyl ether (IBVE) was carried out with use of the HC1-IBVE adduct [1: CH3CH(OiBu)Cl]/Lewis acid (MX") initiating systems in CH2CI2 at -15 °C. Living polymers were obtained with 1 in conjunction with weak Lewis acids such as ZnCl2 and SnBr4; in contrast, the 1/MX" initiating systems with strong Lewis acids (SnCl4, TiCl4, and EtAlCl2) gave nonliving polymers. However, on addition of ammonium salts (nBu4N+Y~) and phosphonium salts (nBu4P+Y) carrying nucleophilic anions (Y~= Cl", Br, I", CH3CO2"), well-defined living polymers were indeed obtained (Mw/Mn ~1.1) with the SnCl4-based system. As model reactions of these living and nonliving polymerizations, a series of mixtures of 1 and MX" in the presence and absence of the salts were analyzed in CH2CI2 at -78 °C or above directly by NMR spectroscopy. Upon mixing SnCl4 with 1, the -methine and the pendant methylene absorptions of 1 shifted remarkably downfield (e.g., up to ca. 10 ppm for the former), and the extent of the downfield shifts increased with increasing SnCl4 concentration. On further addition of the salts with nucleophilic anions, the downfield signals returned to the original upfield position for the covalent adduct 1 alone. Thus, l/SnCl4 generates an ionic growing species that is in a rapid equilibrium with the covalent precursor 1, and the salts suppress the ionic dissociation of the growing carbocation to induce living cationic polymerization.

Poly(diphenylacety1ene) is thermally very stable, but insoluble in any solvent, whereas polyacetylenes from unsymmetrically disubstituted acetylenes are generally soluble. Hence, the synthesis of soluble poly(diphenylacety1enes) was examined by introducing the trimethylsilyl group. 1-Phenyl-2-lp-(trimethylaily1)phenyllacetylene and l-phenyl-2-[m-(trimethylsilyl)phenyl]acetylene polymerized with T a c k cocatalyst systems to provide new polymers with over 70% yields having a weight-average molecular weight over 1 X 106. As cocatalysts, nBurSn, EhSiH, and SBBN were especially effective. The polymers were yellow solids with the alternating double bond structure [-CP~=C(C&S~M~S)-I,,. They completely dissolved in toluene, CHCla, etc., and formed tough f i i by eolution casting. The onset temperatures of weight loss in TGA in air were as high as ca. 400 "C. Their oxygen permeability coefficients were both high, ca. lo00 barrers.