Viscoelastic and electrical transitions in gelation of electrically conducting polyaniline

Mari Tiitu, Panu Hiekkataipale, Juha Hartikainen, Tapio Mäkelä, Olli Ikkala

Research output: Contribution to journalArticleScientificpeer-review

37 Citations (Scopus)

Abstract

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 G0 ∼ |ε|t and s ≈ 1.0−1.2 for the zero shear rate viscosity η0 ∼ |ε|-s where ε = (t − tgel)/tgel. 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.
Original languageEnglish
Pages (from-to)5212-5217
JournalMacromolecules
Volume35
Issue number13
DOIs
Publication statusPublished - 2002
MoE publication typeA1 Journal article-refereed

Fingerprint

Gelation
Polyaniline
Evaporation
Aging of materials
Conducting polymers
Polymethyl Methacrylate
Sols
Shear deformation
Viscosity
Acids
Fluids
polyaniline

Keywords

  • gelation
  • sol-gel
  • polyaniline

Cite this

Tiitu, Mari ; Hiekkataipale, Panu ; Hartikainen, Juha ; Mäkelä, Tapio ; Ikkala, Olli. / Viscoelastic and electrical transitions in gelation of electrically conducting polyaniline. In: Macromolecules. 2002 ; Vol. 35, No. 13. pp. 5212-5217.
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abstract = "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 G0 ∼ |ε|t and s ≈ 1.0−1.2 for the zero shear rate viscosity η0 ∼ |ε|-s where ε = (t − tgel)/tgel. 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.",
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Viscoelastic and electrical transitions in gelation of electrically conducting polyaniline. / Tiitu, Mari; Hiekkataipale, Panu; Hartikainen, Juha; Mäkelä, Tapio; Ikkala, Olli.

In: Macromolecules, Vol. 35, No. 13, 2002, p. 5212-5217.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Viscoelastic and electrical transitions in gelation of electrically conducting polyaniline

AU - Tiitu, Mari

AU - Hiekkataipale, Panu

AU - Hartikainen, Juha

AU - Mäkelä, Tapio

AU - Ikkala, Olli

PY - 2002

Y1 - 2002

N2 - 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 G0 ∼ |ε|t and s ≈ 1.0−1.2 for the zero shear rate viscosity η0 ∼ |ε|-s where ε = (t − tgel)/tgel. 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.

AB - 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 G0 ∼ |ε|t and s ≈ 1.0−1.2 for the zero shear rate viscosity η0 ∼ |ε|-s where ε = (t − tgel)/tgel. 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.

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KW - sol-gel

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