Abstract
| Original language | English |
|---|---|
| Pages (from-to) | 5212-5217 |
| Journal | Macromolecules |
| Volume | 35 |
| Issue number | 13 |
| DOIs | |
| Publication status | Published - 2002 |
| MoE publication type | A1 Journal article-refereed |
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Keywords
- gelation
- sol-gel
- polyaniline
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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 journal › Article › Scientific › peer-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.
KW - gelation
KW - sol-gel
KW - polyaniline
U2 - 10.1021/ma011943z
DO - 10.1021/ma011943z
M3 - Article
VL - 35
SP - 5212
EP - 5217
JO - Macromolecules
JF - Macromolecules
SN - 0024-9297
IS - 13
ER -