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Time‐dependent nonlinear optical properties of pyroelectric liquid crystalline polymers
Author(s) -
Örtegren Jonas,
Busson Philippe,
Gedde Ulf W.,
Hult Anders,
Eriksson Anders,
Lindgren Mikael,
Arntzén PerOtto,
Hermann David S.,
Rudquist Per,
Lagerwall Sven T.
Publication year - 1999
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19991480115
Subject(s) - polymer , mesogen , materials science , monomer , acrylate polymer , photopolymer , yield (engineering) , acrylate , polymer chemistry , liquid crystal , second harmonic generation , pyroelectricity , nonlinear optical , nonlinear system , liquid crystalline , chemical engineering , composite material , optics , ferroelectricity , optoelectronics , laser , physics , dielectric , quantum mechanics , engineering
Highly oriented pyroelectric liquid‐crystalline polymers were prepared by photopolymerization under the influence of a static electric field from binary mixtures of two acrylate monomers exhibiting chiral smectic C mesomorphism. Both monomers contained nitro groups to yield second order nonlinear optical properties (second harmonic generation) and one of the monomers had two functional groups to yield a crosslinked polymer. The room temperature second order nonlinear susceptibility of the polymers showed during the first two hours a 10 % decrease after which it remained constant during the next 48 days. At elevated temperatures there was a significant difference in the nonlinear optical properties over time between crosslinked and uncrosslinked polymers. The uncrosslinked polymer showed a pronounced loss of second order nonlinear optical activity with time at ≥38°C. The crosslinked polymer showed a much smaller and basically a temperature independent decrease rate in the second order nonlinear optical properties at all the ageing temperatures (23‐130°C). Both the loss in mesogen order parameter, very evident for the uncrosslinked polymer, and conformational changes occurring within the mesogens (β mechanism), may account for the observations made.