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  • The effect of pyridine ring functionalization on the conductivity of crosslinked co-poly(styrene-4-vinylpyridine) derivatives
    Sever Škapin, Andrijana ; Zupan, Marko, 1947- ; Pejovnik, Stane
    The effect of pyridine ring functionalization in crosslinked co-poly(styrene-4-vinylpyridine) on electrochemical behaviour was studied using impedance spectroscopy. The introduction of a substituent ... on the nitrogen atom increases conductivity from ▫$10^{-14}$▫ to around ▫$10^{-11}$▫ Scm▫$^{-1}$▫ at room temperature, but the effect of the substituent becomes more evident at ▫$^oC$▫, at which the N-butyl derivative (co-poly[styrene-[4-vinyl(N-butylpyridinium bromide)]])-(3) has a higher conductivity (▫$\sigma$▫ = 7 x ▫$10^{-10}$▫ Scm▫$^{-1}$▫ than the hydrogen analog (co-poly[styrene-[4-vinyl(pyridinium bromide)]])-(2) (▫$\sigma$▫ = 4.3 x ▫$10^{-10}$▫ Scm▫$^{-1}$▫), while the iodo derivative (co-poly-[styrene-[4-vinyl(N-iodopyridinium bromide)]])-(6) has a conductivity ten times lower. Further increase in the conductivity was observed upon the substitution of the bromine anion with the three-bromide anion (▫$Br_3)^-$▫, but the effect depends on the substituent on the nitrogen atom: 4.4 times higher conductivity was found for the hydrogen pyridinium salt (4) in comparison with sample (2), and the conductivity increases 30-fold for the N-butyl derivative (5) compared with sample (3). The conductivity increased exponentially with temperature and the activation energy values vary from 0.76 to 1.01 eV. Impedance responses for dried samples of pyridinium salts (2), (3), (4), (5), and (6) suggested electron-type conductivity. The conductivity of crosslinked polymers depends very much on the conditions, and increases by several orders of magnitude when water or methanol is present in the atmosphere during measurements. The conductivity also depends on the stucture of the substituent attached to the nitrogen atom: ▫$\sigma$▫ = 5 x ▫$10^{-4}$▫ Scm▫$^{-1}$▫ and ▫$\sigma$▫ = 2 x ▫$10^{-4}▫$ Scm▫$^{-1}$▫ for hydrogen bromide (2) and N-butyl bromide derivative (3), but the conductivity of the N-iodo derivative (6) changed very little. In contrast, the impedance responses for samples stored in the presence of water or methanol suggested ion conductivity.
    Source: Journal of applied polymer science. - ISSN 0021-8995 (Vol. 61, no. 3, 1996, str. 553-560)
    Type of material - article, component part
    Publish date - 1996
    Language - english
    COBISS.SI-ID - 696602

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