Switchable Response of Ferroelectric Nanoparticle Doped Polymer-Dispersed Liquid Crystals

In this study, we doped polymer-dispersed liquid crystals (PDLCs) with barium titanate (BaTiO₃, BTO) nanoparticles to investigate the effects of particle size on the electro-optical properties of the suspensions, such as the driving voltage and response time. We mixed BTO nanoparticles having various sizes of 8 nm, 20 nm, and 2 μm, and liquid crystals (LCs) (E7) prior to blending the LCs and pre-polymers (NOA 65). We fabricated the PDLC films using the polymerization-induced phase-separation (PIPS) method. The film surface was irradiated with UV (365 nm) light for 3 min to induce phase separation between the LC and the polymer. According to the results, the 10% transmittance voltage (V ₁₀) improved from 18.2 V to 6.8 V by the addition of 0.3 vol% of 8 nm BTO particles to the PDLC. The response time also decreased from 15.2 ms to 8.4 ms. Smaller particles were distributed more uniformly within the sample, which resulted in a reduction of the V ₁₀ and response time of the PDLCs. The results obtained imply that nanoscale ferroelectric particle doping is a powerful tool to tune electro-optical properties of liquid crystals based systems, including improving the electrical performances without compromising other important characteristics, such as the haze of the PDLC devices.