Bistable memory switching of (liquid crystalline copolymer/low molecular weight liquid crystal) composite systems

Bistable electro-optical switching characteristics have been investigated for composite systems in a smectic phase induced by mixing a side chain type nematic liquid crystalline polymer (nematic LCP) or its copolymer with weak polar methoxy terminal groups in the side chains and low molecular weight nematic liquid crystals (nematic LCs) with strong polar cyano end groups. The liquid crystalline copolymer (LCcoP) with weak polar methoxy terminal groups in the side chains attaching to a polysiloxane main chain was used in order to improve the response speed of the bistable light switching for the binary composite system. Although the LCcoP with 52.5 mol% substituted mesogenic side chains did not exhibit any mesophase characteristics at any temperature, this LCcoP induced a smectic state by mixing nematic LCs. A reversible and bistable electro-optical switching with a short response time (approx. 100 ms) was realized for the induced smectic binary composite system upon the application of an appropriate electric field at room temperature.