Selectively deuterated liquid crystalline cyanoazobenzene side-chain polyesters. 3. Investigations of laser induced segmental mobility by Fourier transform infrared spectroscopy

Christian Kulinna, Søren Hvilsted, Claudia Hendann, Heinz W. Siesler, P.S. Ramanujam

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    The laser-induced anisotropy in thin films of an extensive number of cyanoazobenzene sidechain liquid crystalline polytetradecanedioates, -dodecanedioates, and -adipates selectively deuterated at different positions have been investigated with polarized FTIR spectroscopy. The analysis of the segmental orientation based on dichroic ratios of characteristic absorption bands shows that, in polyesters with long main-chain spacing (tetradecanedioates and dodecanedioates), not only the light sensitive azo chromophore but also the main-chain methylene segment and to a smaller extent the flexible spacer are preferentially oriented perpendicular to the laser light polarization. The extent of orientation increases with increasing spacer length. On the other hand, in the shorter adipates only the chromophore and the spacer are likewise oriented. Rapid-scan FTIR analysis performed on-line with the laser irradiation reveals that the alignment of the aliphatic segments arises simultaneously with the chromophore orientation. Temperature dependent infrared investigations of the laser-induced orientation shows that the preservation of the photoinduced anisotropy directly relates to the polyester phase behavior.
    Original languageEnglish
    JournalMacromolecules
    Volume31
    Issue number7
    Pages (from-to)2141-2151
    ISSN0024-9297
    DOIs
    Publication statusPublished - 1998

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