Orientation and anchoring effects in stretched polymer dispersed nematic liquid crystals |
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Authors: | Yue Zhao Shuying Bai Thanh-Nha Banh Julien Brazeau |
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Institution: | Département de Chimie,Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1 |
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Abstract: | The induction of liquid crystal orientation through mechanical stretching was investigated for polymer dispersed liquid crystals (PDLCs) by means of infrared dichroism. Using a nematic liquid crystal BL006 and polyacrylic acid as the polymer matrix, it was possible to stretch the PDLC films with BL006 in either the isotropic or the nematic phase. After cooling the films under strain to room temperature, the molecular orientation of BL006 was found to be much higher for films that contained isotropic liquid droplets of BL006 at the time of stretching than for films that had nematic droplets. Stretching PDLC films with isotropic droplets results in no molecular orientation, but the orientation is induced during the subsequent cooling when BL006 goes through the isotropic-to-nematic phase transition. Interestingly for PAA/BL006, the nematic director orients along the long axes of the elongated droplets despite liquid crystal anchoring perpendicular to the polymer interface. |
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Keywords: | polysilane phase behaviour liquid crystalline polymer (LCP) smectic phase reentrant isotropic phase |
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