In an effort to study viscoelastic (vector) percolation and conductivity (scalar) percolation
within a single system, we demonstrate a conducting polymer/solvent system, which upon gelation
undergoes a viscoelastic transition, followed by a separate conductivity transition. Polyaniline doped by
camphorsulfonic acid, i.e., PANI(CSA)0.5, shows three regimes in mixtures with m-cresol at a narrow
concentration window of ca. 6.5−7.5 wt %. At small aging times, a viscous fluid (sol) is encountered with
poor conductivity. Upon gelation, the system enters a state with elastic behavior but with poor conductivity.
Further aging leads to conductivity percolation with ca. 4 orders of magnitude increase of conductivity.
The scaling exponents for gelation are t ≈ 2.0−2.5 for the equilibrium modulus G
0 ∼ |ε|
t
and s ≈ 1.0−1.2
for the zero shear rate viscosity η0 ∼ |ε|-s
where ε = (t − t
gel)/t
gel. The present observations may also be
relevant in applications to understand the homogeneity of solid films upon solvent evaporation: The
early “trapped” junction zones in gelation can cause the previously observed granular structures in solid
films, if the junction zones grow during the solvent evaporation. This may limit the available conductivity
levels in solid films.
Cylindrical self-assembly and flow alignment of comb-shaped supramolecules of electrically conducting polyaniline Tiitu, M.; Volk, N.; Torkkeli, M.; Serimaa, R.; ten Brinke, G.; Ikkala, O. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. FIN-00014, Helsinki, Finland Received February 6, 2004; Revised Manuscript Received June 24, 2004 ABSTRACT: Electrically conducting hexagonally self-assembled nanostructures of poly(aniline) (PANI) protonated with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) and hydrogen bonded with resorcinol (res), 4-ethylresorcinol (C 2res) or 4-hexylresorcinol (C6res) are studied. Small-angle X-ray scattering (SAXS) of PANI(AMPSA)0.5(Cnres)y with y ) 0, ..., 1.5 indicate cylindrical self-assembly in all cases, and the long period depends on n and y. Addition of Cnres leads to plasticization and an increase of conductivity of up to ca. 4 orders of magnitude until saturation is achieved upon approaching y ) 1. Simultaneously, the temperature gradient of the conductivity dσ/dT near the room temperature changes from positive to negative, which is reminescent to a transition from a thermally activated hopping-type to a more "metallic-like" behavior. It is suggested that, upon complexation with especially res and C2res, the PANI chains become progressively more confined in cylinders suggesting their stretching. Overall alignment of the local self-assembled domains was also aimed. In films, anisotropic overall structure and conductivity are observed upon pressing the "melt" samples between two glass plates. In more bulky samples, so far, large amplitude oscillating shear flow leads to biaxial structural anisotropy without observable conductivity anisotropy, potentially indicating the importance of residual defects for the transport properties.
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