Polymer dispersed liquid crystals (PDLC) have been heavily researched for applications such as smart windows in buildings, displays, and automobiles. A large focus on improving smart window production is in the reduction of production cost and required power. Here, the developed PDLC provides transmittance contrast ratios up to 30, with required power on the order of micro-Watts. Our smart PDLC windows can maintain a steady state of high transparency in DC field application and does not require high power (milliWatt), high frequency AC fields like conventional PDLCs with similar contrast ratios. When using commercially available pre-polymer, significant relaxation of the transparent state back to a translucent or opaque state occurs when holding a voltage at a steady state for a few seconds. This phenomenon occurs increasingly so at lower voltages (10V), as determined via UV-VIS (transmission) and custom color difference quotient (reflection) characterization techniques. To further understand and improve relaxation with DC voltage application, a series of photosensitive acrylate-based pre-polymer chemistries similar to PN393 were formulated and tested. Each formulation component has been systematically modified and characterized via the aforementioned characterization techniques in conjunction with scanning electron microscopy and UV-Rheology in a trend towards decreasing the power requirements and reducing electro-optical relaxation with DC field application. With polymerization induced phase separation speeds completing within two seconds in response to 365nm light, such a formulation can be incorporated into a roll-to-roll production method and thus can be utilized for flexible electronics.
Prepared by LLNL under Contract DE-AC52-07NA27344.