Investigation of chromophore-chromophore interaction by electro-optic measurements, linear dichroism, x-ray scattering, and density-functional calculations

D. Apitz*, R. P. Bertram, N. Benter, W. Hieringer, J. W. Andreasen, M. M. Nielsen, P. M. Johansen, K. Buse

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

38 Citations (Scopus)

Abstract

Free-beam interferometry and angle-resolved absorption spectra are used to investigate the linear electro-optic coefficients and the linear dichroism in photoaddressable bis-azo copolymer thin films. From the first- and second order parameters deduced, the chromophore orientation distribution is calculated and displayed for several poling temperatures and chromophore concentrations. The influence of dipole-dipole interaction on the overall polymer dynamics is discussed. The first order parameter, and therefore the Pockels effect, peaks for a poling temperature of around 10°C above the glass transition. The decrease of the Pockels effect above this temperature region is triggered by a head-to-tail chromophore orientation, i.e., a transition to a microcrystalline phase, increasing the second order parameter. Comparison of the experimentally observed absorption spectra and those obtained by density-functional calculations support the picture of differently aligned bis-azo dye molecules in a trans,trans configuration. Complementary wide-angle x-ray scattering is recorded to confirm the various kinds of ordering in samples poled at different temperatures.

Original languageEnglish
Article number036610
JournalPhysical Review E (Statistical, Nonlinear, and Soft Matter Physics)
Volume72
Issue number3
Number of pages10
ISSN1539-3755
DOIs
Publication statusPublished - 1 Sept 2005
Externally publishedYes

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