Title: Electro-optical memory of a nematic liquid crystal doped by multi-walled carbon nanotubes
Author(s):

	L. Dolgov (Institute of Physics, Nat. Acad. of Sci. of Ukraine, 46 Nauki Prospect, 03680 Kyiv, Ukraine) ,
	O. Yaroshchuk (Institute of Physics, Nat. Acad. of Sci. of Ukraine, 46 Nauki Prospect, 03680 Kyiv, Ukraine) ,
	S. Tomylko (Institute of Physics, Nat. Acad. of Sci. of Ukraine, 46 Nauki Prospect, 03680 Kyiv, Ukraine) ,
	N. Lebovka (Institute of Biocolloidal Chemistry named after F.D. Ovcharenko, Nat. Acad. of Sci. of Ukraine, 42 blvd. Vernadskogo, Kyiv 03142, Ukraine)

A pronounced irreversible electro-optical response (memory effect) has been recently observed for nematic liquid crystal (LC) EBBA doped by multi-walled carbon nanotubes (MWCNTs) near the percolation threshold of the MWCNTs (0.02÷0.05 wt. %). It is caused by irreversible homeotropic-to-planar reorientation of LC in an electric field. This feature is explained by electro-hydrodynamically stimulated dispergation of MWCNTs in LC and by the formation of a percolation MWCNT network which acts as a spatially distributed surface stabilizing the planar state of the LC. This mechanism is confirmed by the absence of memory in the EBBA/MWCNT composites, whose original structure is fixed by a polymer. The observed effect suggests new operation modes for the memory type and bistable LC devices, as well as a method for \textit{in situ} dispergation of carbon nanotubes in LC cells.

Key words: carbon nanotubes, liquid crystal, memory effect
PACS: 42.70.Df, 42.79.Kr, 77.22.Ch, 77.84.Lf, 81.07.De

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