Asha Kumari

Liquid crystal (LC) droplets are promising candidates for sensing applications due to their high sensitivity to surface anchoring changes, resulting in readily detectable optical effects. Herein, we have designed and synthesized amino acid-based bottlebrush polymers and investigated their impact on LC director configurations in the droplets. The pseudopeptidic bottlebrush polymers with an aromatic (phenyl) and aliphatic appendages are synthesized using ring-opening metathesis polymerization (ROMP). Polymer dispersed liquid crystal (PDLC) samples are prepared by employing pseudopeptidic bottlebrush polymers and 4-cyano-4′-pentylbiphenyl (5CB) LC via solvent-induced phase separation (SIPS) technique. Due to π–π stacking, the phenyl group favours radial configuration, whereas the repulsion between 5CB and aliphatic groups induces molecular alignment leading to bipolar droplet arrangement. The impact of various pendant groups attached to the polymer on the prepared PDLC sample's surface characteristics and free energy components is illustrated. The sensing capability of 5CB dispersed in pseudopeptidic bottlebrush polymers for various pH solutions is investigated using polarizing optical microscopy (POM). The PDLC samples are moderately permeable to water and sensitive to different pH solutions. The results demonstrate a simplified and straightforward approach for preparing LC-based biosensors and chemical sensors.

The physical properties of polymer dispersed liquid crystals (PDLC) can be tuned as per the application requirement by controlling their composition ratio and microstructure. The addition of nanoparticles is the most convenient method to engineer the properties of PDLCs. This paper investigates the effects of barium titanate (BaTiO₃) nanoparticle doping on the morphology, electro-optic, and optical properties of PDLC films. The epoxy resins based PDLC films prepared by polymerisation induced phase separation via heat curing method are doped with BaTiO₃ nanoparticle for the first time. The impact of BaTiO₃ nanoparticle on the microstructure was studied using polarising optical microscopy and scanning electron microscopy. The electro-optic study reveals that the addition of BaTiO₃ nanoparticle results in the reduction of rise time, threshold voltage, saturation voltage and enhancement in the contrast ratio. The doping also results in a decrement of the off-state transmittance curve and an increment in the UV-Visible absorption spectrum. The development of BaTiO₃ doped PDLC films with faster rise time, lower threshold voltage, lower saturation voltage and better contrast ratio will significantly enhance the potential technological applications of PDLC-based devices for smart windows, sensors and flexible devices.