Rheo-optics of a conjugated polymer system in shear

The polymeric chromophore, poly(4-butoxycarbonylmethylurethane), p-4BCMU, h as a diacetylene backbone that displays a broad range of optical properties directly attributed to its conformation. The W-Vis spectral properties of the polymer solution are dependent upon the backbone conjugation length, wh ich describes the length over which the pi -electrons are delocalised. The persistence length of the polymer chain describes the curvature of the poly mer chain and is dependent upon the solvent quality and thermal properties of the system. Changes in persistence length, which are accompanied by a ch ange in polymer conformation, lead to changes in the conjugation length and , therefore, the measured absorption spectra. However, under an applied she ar force, the persistence length of the polymer chain is assumed, through k inetic theories, to remain constant even though the polymer chain may chang e conformation. A novel rheo-optic experimental system was developed, where a wavelength region of Light about the absorption maximum of the polymer b ackbone is scanned for each shear rate. From the experimental results it wa s confirmed that while the polymer chain segments aligned in the shear dire ction, there was no change in the polymer chain persistence length with she ar, which is consistent with kinetic theory. (C) 2001 Elsevier Science Ltd. All rights reserved.