Liquid crystal alignment in electro-responsive nanostructured thermosetting materialsbased on block copolymer dispersed liquid crystal

Abstract

Novel well-defined nanostructured thermosetting systems were prepared by modification ofa diglicydylether of bisphenol-A epoxy resin (DGEBA) with 10 or 15 wt% amphiphilicpoly(styrene-b-ethylene oxide) block copolymer (PSEO) and 30 or 40 wt% low molecular weight liquid crystal4′-(hexyl)-4-biphenyl-carbonitrile (HBC) using m-xylylenediamine (MXDA) as a curingagent. The competition between well-defined nanostructured materials and the ability foralignment of the liquid crystal phase in the materials obtained has been studied by atomicand electrostatic force microscopy, AFM and EFM, respectively. Based on our knowledge,this is the first time that addition of an adequate amount (10 wt%) of a block copolymer to40 wt% HBC–(DGEBA/MXDA) leads to a well-organized nanostructured thermosettingsystem (between a hexagonal and worm-like ordered structure), which is alsoelectro-responsive with high rate contrast. This behavior was confirmed using electrostaticforce microscopy (EFM), by means of the response of the HBC liquid crystal phase to thevoltage applied to the EFM tip. In contrast, though materials containing 15 wt%PSEO and 30 wt% HBC also form a well-defined nanostructured thermosettingsystem, they do not show such a high contrast between the uncharged and chargedsurface.