Despite nearly three decades of materials development, the transport properties in the 'metallic state' of the so-called conducting polymers are still not typical of conventional metals. The hallmark of metallic resistivity--a monotonic decrease in resistivity with temperature--has not been obtained at temperatures over the full range below room temperature; and a frequency dependent conductivity, sigma(omega), typical of metals has also not been observed. In contrast, the low-temperature behaviour of 'metallic' polymers has, in all previous cases, exhibited an increase in resistivity as temperature is further decreased, as a result of disorder-induced localization of the charge carriers. This disorder-induced localization also changes the infrared response such that sigma(omega) deviates from the prediction of Drude theory. Here we report classic metallic transport data obtained from truly metallic polymers. With polyaniline samples prepared using self-stabilized dispersion polymerization, we find that for samples having room-temperature conductivities in excess of 1,000 S cm(-1), the resistivity decreases monotonically as the temperature is lowered down to 5 K, and that the infrared spectra are characteristic of the conventional Drude model even at the lowest frequencies measured.
Out of the blue: A reversible temperature‐dependent change in the absorption characteristics of spin‐coated terephthalic acid/diacetylene polymers is observed. The polymer is prepared by topochemical photopolymerization of the diacetylene side chains of the stacked terephthalic acid units (see picture). The absorption bands of the polymeric product move reversibly from 640 nm (blue form of the polymer) to 580 nm (red form) during heating–cooling cycles.
A soluble polyaniline (PANi) was synthesized by modifying with a photolabile, acid-labile, and thermolabile tert-butoxycarbonyl (t-BOC) group in this study. The prepared PANi(t-BOC) is highly soluble and thermodynamically stable in low-boiling solvents such as THF, dioxane, and CHCl 3. This soluble form of PANi(t-BOC) was converted to the insoluble and electrically conductive emeraldine salts upon photodoping with only a catalytic amount of photoacid generators such as N-(tosyloxy)-or (camphorsulfonyloxy)norborneneimide or -onium salts. As a result of this solubility difference, conducting patterns of high resolution were produced by conventional photolithography process. Further, upon removal of the t-BOC groups in PANi(t-BOC) by acid doping, no obvious morphology change of the films was observed, and such conversion recovered the original conductivity level of the doped PANi. Since the t-BOC protecting groups are easily removed in doping or acid-catalyzed reaction by chemical amplification or thermal bake, the PANi(t-BOC) can be used as conductive matrix polymers for negative type photoimaging or printing materials or for novel solution-processed applications in various microelectronic devices.
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