Solvent dependence polyacetylenes

Figure 2. NMR spectra of methanol-d/chloroform-d solutions of an L-leucine-containing polyacetylene (le 50 mg/mL) with varying ratios of methanol-d4 (vol %) (A) 20, (B) 40, (C) 60, and (D) 80, Insert solvent dependence of the chemical shift of the amide proton resonance of le and its monomer 23 (50 mg/mL) in methanol-dychloroform-d mixtures. The resonance peaks of the amide (HNCO) and vinyl (HC-) protons are respectively marked with downward arrows (>l) and open circles (o), while those of the solvents are marked with asterisks ( ),...

Figure 4. Solvent dependence of the first Cotton effect (X ax nm) of the polyacetylenes bearing pendants of L-amino acid methyl esters.

Figure 8 Thickness dependence of total shielding efficiency (SET) of highly conducting polymers (A) stretched heavily iodine doped Tsukamoto polyacetylene, (B) camphor sulfonic acid doped polyaniline cast from m-cresol solvent, (C) PFg doped polypyrrole.

Figure 8.1. Thickness dependence of total Shielding Efficiency (SE,) of highly conducting polymers measured at 6.5 GHz (from [23c]) sample A stretched heavily iodine doped Tsukamoto polyacetylene (dotted line is obtained by using calculation of Se, with approximated values of a absorption coefficient and n) sample B unstretched heavily iodine doped Tsukamoto polyacetylene sample C camphor sulphonic acid doped polyaniline in m-cresol solvent sample D PFe doped polypyrrole sample E TSO doped polypyrrole Inset comparison of (microwave conductivity), c, and tan 6, Reprinted from ref. 23c with permission. Copyright American Institute of Physics.

Cao et al. [133] studied the air stability of re-doped polythiophene which was prepared electrochemically and then compensated by aqueous ammonia as detailed in Table 16.8. Ammonia-compensated polythiophene was found to be quite stable when stored in an ambient atmosphere for 3 months, as neither any weight gain nor any change in infra-red spectmm was observed. Both the chemically re-doped and electrochemically prepared polythiophene showed much better stability as compared to polyacetylene and the air stability of the polymer was found to be dependent on the doping counter-ion as well as the solvent used in electrochemical polymerization. Electrochemically prepared polythiophene from a mixture of CH3CN and CH3NO2 (1 1 by volume) maintained their electrical conductivity, whereas the polymer re-doped chemically by FeCls was observed to be most stable in ambient air. 

A group of new amphiphilic macromolecules comprised of hydrophobic polyacetylene backbone and hydrophilic pendant groups of naturally occurring species such as amino acids, saccharides, and nucleosides are synthesized. The polymers exhibit solvatochromism. The macromolecular chains show helical confommtions that depend on the molecular structures of the pendants, solvent, temperature, pH, and additives. 

Tensile drawing of the wet polyacetylene films yielded a maximum stretching ratio of about 15 for the thick films and about 10 for thin films. By contrast, fully dried polyacetylene films could not be extended beyond 6 times their original length under otherwise similar experimental conditions. Some variation in the maximum stretching ratio, Xmax. was found, dependent on the characteristics of the liquid used as "plasticizer . Specifically, it was observed that Xmax was dependent on the boiling point and the specific composition in the case of mixed liquids. The results seem to indicate that Xmax is dependent on the relative content of solvent in the film and on the speed of evaporation of the solvent from bulk of the film. Hexadienes, for example, were found to be excellent plasticizers for polyacetylene, presumably due to the easier penetration of these liquids into the polyacetylene lattice because of the similarity in molecular structures. Pure aromatic solvents appeared to be the least effective however, a 4 1 mixture of toluene and cumene yielded excellent results. 

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