Stabilization of cholesteric blue phases using polymerized nanoparticles

This study explores the roles of UV-polymerizable silicon-based nanoparticles in polymer-stabilized blue phase (PSBP) liquid crystals. Our analysis reveals that the polymerized polymer leads to widening of the temperature range of the blue phase and stabilization of the reflection wavelength against temperature variations. A polymer morphology study of PSBP reveals the polydomain nature of the blue phase. In practical application, the advantage of the low-surface-energy property of the UV-polymerizable silicon-based nanoparticles leads to a significant reduction in switching voltage from 140 to 40 V.

Figure 1

(a) POM images of BP textures of sample 4 at (1) 44.5 °C, (2) 38 °C, (3) 23 °C, (4) 17 °C, and (5) 16 °C, after polymerization. The scale bar is 20 μm. (b) Reflection spectra of pure BPLC without monomer. (c) Plot of wavelength versus temperature for samples 1 (at 570 nm), 2 (at 574 nm), 3 (at 570 nm), and 4 (at 576 nm) after polymerization.

Figure 2

(a) Normalized transmittance-voltage (TV) curves of samples 1 (at 45 °C), 2 (at 45 °C), 3 (at 45 °C), 4 (at 35 °C), and sample containing mixture of BL006 and MCL6080 (at 40 °C without monomer). The BP temperature range increased to a higher temperature than that for the mixture before polymerization. (b) Plot of transmittance versus response time for sample 4.

Figure 3

POM images of PSBP cell of sample 1 (6% polymer) under applied voltage of (a) 0 V, (b) 20 V, (c) 30 V, (d) 40 V, (e) 50 V, (f) 60 V, (g) 70 V, (h) 80 V, (i) 100 V with respect to the crossed polarizers labeled A and P at 45 °C. The black scale bar is 50 μm. A further increase in applied voltage causes a small shift in the spectral wavelength and increases light transmission for the samples.

Figure 4

POM images of PSBP cell of sample 4 (10% polymer) under applied voltage of (a) 0 V, (b) 20 V, (c) 30 V, (d) 40 V, (e) 50 V, (f) 60 V, (g) 70 V, (h) 80 V, (i) 100 V with respect to the crossed polarizers labeled A and P at 35 °C. The black scale bar is 50 μm. A further increase in applied voltage causes a small shift in the spectral wavelength and increases light transmission for the samples.

Figure 5

SEM micrographs of polymer morphology of PSBP cell of sample 4: (a) Surface of a substrate with electrode (the arrow indicates the electrode direction, which is the preferential orientation of polymer sticks), (b) surface of a substrate without electrode. The scale bars are 2 μm. (c) Simulated polymer network structure within a cubic lattice of a polymer-stabilized blue phase (the small cubes in the right-hand side image represent PSS-PMH).