Control homogeneous alignment of chiral nematic liquid crystal with smectic-like short-range order by thermal treatment

This study indicated that the smectic-like short-range order (SSO) provided an opportunity to improve the planar orientation of chiral nematic liquid crystal (N*-LC) molecules while increasing the light transmittance of the N*-LC cells. The SSO formed between N*-smectic A (SmA) transition was first introduced into N*-LC compositions and then applied a specific thermal process at the temperature of SSO (TSSO). Finally, the uniform alignment of the N*-LC molecules was obtained. Decreasing the heating rate and extending the holding time at TSSO were effective at reducing the oily streak and perfecting the planar texture of the N*-LC cells. And this method was also resultful for N*-LC composites exhibited different pitches.

The method of improving the homogeneous alignment of chiral nematic liquid crystal by thermal treating at the temperature of smectic-like short-range order was put forward. The effect of holding time and heating rate on the improvement of homogeneous alignment was investigated by comparing the experimental result of different thermal treating processes.Figure optionsDownload as PowerPoint slideHighlights
► The smectic-like short-range order was formed towards the SmA-N* phase transition.
► Thermal treating at the temperature of smectic-like short-range order improved the homogeneous alignment of N* liquid crystal.
► Slowing down the heating rate and extending the holding time were good for improving the homogeneous alignment.
► The mechanism relied on the special structure of smectic-like short-range order formed near SmA-N* phase transition.