Thermoreversible gelation of regioregular poly(3-hexylthiophene) in xylene

Malik, Sudip ; Jana, Tushar ; Nandi, Arun K. (2001) Thermoreversible gelation of regioregular poly(3-hexylthiophene) in xylene Macromolecules, 34 (2). pp. 275-282. ISSN 0024-9297

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Official URL: http://pubs.acs.org/doi/abs/10.1021/ma000977o

Related URL: http://dx.doi.org/10.1021/ma000977o

Abstract

Regioregular poly(3-hexylthiophene) (P3HT) produces thermoreversible gel in xylene. The gel is brownish-red in color. SEM and TEM studies indicate the presence of fibrillar network. WAXS and electron diffraction pattern indicate the presence of P3HT crystallites in the gel. The gels exhibit a first-order phase transition when heated in DSC. A time-dependent UV-vis study indicates that gelation in this system is probably accompanied by two different processes, e.g., (1) coil-to-rod transformation and (2) aggregation of rods to form the crystallites producing the gel. The gelation rate (tgel-1) measured from the test tube tilting method is analyzed using the equation tgel-1 = f(C) f(T), where f(c) = φn, φ being the reduced overlapping concentration and n is an exponent. The average "n" value determined is 0.52, which indicates that three-dimensional percolation is a suitable model for this gelation. The gelation rate is analyzed according to the Flory-Weaver theory of coil-to-helix transition, and the free energy of activation (ΔF) for the coil-to-rod transformation is found to be 23.7 kcal/mol. It is also analyzed using the theory of fibrillar crystallization in solution, and the free energy of formation of critical size crystalline nucleus (ΔGdil) is found to be 37.5 kcal/mol. The conductivity of the dried P3HT gel becomes enhanced by ~10 times that of the cast film in the undoped state, but in the doped state there is an ~50-fold increase.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:24102
Deposited On:29 Nov 2010 10:26
Last Modified:08 Jun 2011 07:00

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