Effect of an additive on the permanent memory effect of polymer dispersed liquid crystal films

Abstract

BACKGROUND Polymer dispersed liquid crystal (PDLC) films have a range of applications varying from switchable windows to new optical memory devices. They switch from an opaque state, when liquid crystal molecules are randomly dispersed, to a transparent state, when liquid crystal molecules are aligned, simply by applying a small voltage. On some PDLC films, the transparent state is retained even when the voltage is switched off; this is called permanent memory effect (PME). This process is totally reversible, returning to the initial opaque state either through heating or applying a higher frequency electric field when using a two frequency liquid crystal. RESULTS In this work, the impact on the electro-optical response of PDLC films as a result of adding an additive was studied. This performance is affected by several factors, the most important being the anchorage force. This anchorage force is modified with the addition of an additive such as TX-100. As a result, it was verified that the addition of TX-100, increased the PME up to 98.7% and decreased the voltage required to achieve 90% of maximum transmittance to 2 V µm−1. CONCLUSIONS The addition of a surfactant, as TX-100 in this case, was shown to be a valuable method to control the PME in PDLC systems in particular those prepared by PIPS from the oligomer polyethylene glycol dimethacrylate and the monomer triethylene glycol dimethacrylate in mixture with the nematic LC E7. This new advance on liquid crystal field also allows development of a new memory device based on a write–read–erase cycle. © 2015 Society of Chemical Industry