Effects of chemical structure and composition of the polymer matrix on the morphology and electro-optical performance of polymer-dispersed liquid crystal films

Abstract

Polymer-dispersed liquid crystal (PDLC) systems on the basis of nematic liquid crystal E7 and amphiphilic binary copolymers of acrylic acid (AA) with such acrylates as 2-ethylhexyl acrylate (EHA), n-butyl acrylate (BA), and methyl acrylate (MA) are investigated. It is shown that the liquid crystal (LC) drops in the copolymer EHA–AA have submicrometre sizes, and their dependence on the composition of the photo-curable monomer mixture is described by a parabolic curve. The highly oriented domain structure in the same system is first revealed when electric field is applied. The threshold voltage for all systems begins to increase with some critical composition of a monomer mixture in which the longer the hydrocarbonic radical in an acrylate molecule, the higher the content of AA. The PDLC system based on the BA–AA copolymer with 30 wt% LC exhibits the least value of the driving voltage, 1 V μm^–1, and the lowest memory effect.

Keywords:

• polymer-dispersed liquid crystal
• photo-polymerisation
• acrylic monomers
• electo-optical properties
• morphology

Acknowledgements

This work was financially supported by the Analytical Special Purpose Program Development of the Scientific Potential of the Higher School (2009–2010) (project 2.1.1/1473), and Federal Special Purpose Program ‘Scientific and Educational Staff of Innovative Russia’ (2009–2010) (project 14.740.11.0481), Russia. We also greatly thank collaborators of Institute for Physics of Microstructures RAS for SEM measurements of the PDLC films.