Kinetics study of phase separation in polyacrylic acid/nematic LC system by optical technique

Maria Mucha; Z. Krolikowski

doi:10.1117/12.472197

27 June 2002 Kinetics study of phase separation in polyacrylic acid/nematic LC system by optical technique

Maria Mucha, Z. Krolikowski

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 T_I of the liquid crystal. An increase of the initiator amount shortens the time of polymerization (t_i), 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%, w_t(i) equals 1%, polymerization temperature T_p equals 100 - 110 degree(s)C.

Citation Download Citation

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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