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27 June 2002 Kinetics study of phase separation in polyacrylic acid/nematic LC system by optical technique
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Proceedings Volume 4759, XIV Conference on Liquid Crystals: Chemistry, Physics, and Applications; (2002) https://doi.org/10.1117/12.472197
Event: XIV Conference on Liquid Crystals, Chemistry, Physics, and Applications, 2001, Zakopane, Poland
Abstract
Thin polymer layers containing liquid crystal LC of non- linear optical properties were obtained from polyacrylic acid. Samples were produced by phase separation as a consequence of chemical polymerization (PIPS method) resulting in precipitation of liquid crystals in the form of droplets in a polymer matrix being formed. Films were produced in variable conditions of polymerization time and temperature and different content of an initiator (1 - 3 wt%). They contained of 10 - 40 wt% of LC. The cell thickness was constant and equal to 20 micrometers . Systems obtained in this way were subjected to thermo-optical and electro-optical studies, morphological structure investigation and DSC analysis. The polymerization time has a significant influence on the size and number of LC droplets. The presence of benzoyl peroxide can cause partial destruction of LC properties which is reflected by a decrease of isotropization temperature TI of the liquid crystal. An increase of the initiator amount shortens the time of polymerization (ti), while process enthalpy ((Delta) H) increases. Hence, the liquid crystal separation time decreases as well. Films prepared by this method present good electro-optical properties. Rise and decay times of orientation are short and equal to 2 - 17 ms (depending on driving voltage applied) and about 80 ms, respectively. Threshold voltage for the best sample is equal to 5 V. Optimal conditions are found: LC content equals 20%, wt(i) equals 1%, polymerization temperature Tp equals 100 - 110 degree(s)C.
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Maria Mucha and Z. Krolikowski "Kinetics study of phase separation in polyacrylic acid/nematic LC system by optical technique", Proc. SPIE 4759, XIV Conference on Liquid Crystals: Chemistry, Physics, and Applications, (27 June 2002); https://doi.org/10.1117/12.472197
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