Effects of acrylate monomers with different alkyl chain structure on the electro-optical properties and microstructure of polymer dispersed liquid crystals

Polymer dispersed liquid crystals (PDLCs) have shown great potential in applications, such as displays and smart windows. However, the driving voltage and contrast ratio are still far from requirement. In this work, acrylate monomers with different alkyl chains were applied to prepare PDLC films. Then the electro-optical performance and microstructure were characterized and compared. Results show that the contrast ratio can be improved by nearly 50% through adjusting the alkyl chain length. Meanwhile, the slightly increased driving voltages can be compensated by introducing branched chains. Contrarily, isomeric structure with more branched chains but short chain length would not contribute much. The chain structure can affect the phase separation process and furtherly the interaction between polymer matrix and liquid crystal droplets. Finally, an optimized PDLC film with high contrast ratio over 100 was demonstrated, which showed two distinct states: highly transparent state with transmittance over 87% at a 0.52 V μm −1 electric field and strong scattering state with transmittance less than 1% in the absence of an electric field. It is anticipated that the research can provide more design choices from material perspective and pave the way for further industrial utilizations of PDLC films.