Model for Conformational Relaxation of Flexible Conjugated Polymers: Application to p-Phenylenevinylene Trimers in Nonpolar Solvents

Authors

  • Dr. Adelino M. Galvão,

    Corresponding author
    1. Centro de Química Estrutural, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais s/n, 1049-001 Lisbon (Portugal)
    • Centro de Química Estrutural, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais s/n, 1049-001 Lisbon (Portugal)
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  • Dr. Roberto E. Di Paolo,

    1. Centro de Química Estrutural, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais s/n, 1049-001 Lisbon (Portugal)
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  • Prof. António L. Maçanita,

    1. Centro de Química Estrutural, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais s/n, 1049-001 Lisbon (Portugal)
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  • Prof. K. Razi Naqvi

    1. Department of Physics, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway)
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Abstract

Photoexcitation of flexible conjugated polymers is invariably followed by a fast conformational/torsional relaxation towards a configuration favouring coplanarity of the conjugated segments. In general, the experimental relaxation rate constant (kCR) depends on the solvent viscosity (η) and temperature (T), and is not proportional to T/η. A theory capable of explaining the observed dependence of kCR on T and η over a wide range of these variables is not available. This gap is filled here by presenting a stochastic model that includes the participation of the oligomer side chain in storing and dissipating the stresses induced by photoexcitation. The model is able to account for the softening of solute–solvent interactions and its predictions are found to be in excellent agreement with the observed relaxation rate constants of a series of substituted p-phenylenevinylene trimers [ChemPhysChem 2009, 10, 448–454] on T, η and the size of the side-chains.

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