Stability of nonlinear optical characteristics and dielectric relaxations of poled amorphous polymers with main-chain chromophores

I. Teraoka, D. Jungbauer, B. Reck, D. Y. Yoon, R. Twieg, C. G. Willson

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We have studied second-order nonlinear optical properties and dielectric relaxation characteristics for two amorphous epoxy polymers based on bisphenol-A with nitroaniline-type nonlinear optical moieties covalently attached as part of the main chain. The nonlinearities, rather large immediately after corona poling, undergo a slow decay at ambient temperature (e.g., ∼29% reduction in the nonlinear coefficient d33 in 28 days), even though the nominal glass transition temperature Tg is ∼80 °C. In dielectric relaxation measurements, both the unpoled and poled samples exhibit two relaxation modes: an α relaxation attributed to glass transition and a β relaxation due to local segmental motions of the main chain. Surprisingly, the critical temperature T associated with the glass transition, obtained by a WLF [M. L. Williams, R. F. Landel, and J. P. Ferry, J. Am. Chem. Soc. 77, 3701 (1955)] fit of the α relaxation characteristics, shows a significant decrease (as much as 40 °C) with increasing poling field. Moreover, the relaxation times of temporal decay of field-induced alignment at ambient temperature, as determined from the stretched exponential function fit of birefringence changes, are found to be consistent with extrapolations from the the dielectric α relaxation characteristics of poled samples.

Original languageEnglish (US)
Pages (from-to)2568-2576
Number of pages9
JournalJournal of Applied Physics
Issue number4
StatePublished - Dec 1 1991


ASJC Scopus subject areas

  • Physics and Astronomy(all)

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