Photo- and thermal switching of blue phase films reflecting both right- and left-circularly polarized light

Abstract

A new kind of blue phase (BP) liquid crystal (LC) films which could reflect both right- and left-circularly polarized light and photo- and thermal switching performance has been demonstrated.

Electrically Switchable, Hyper‐Reflective Blue Phase Liquid Crystals Films

“…Compared to a previously reported BPLC film consisting of a R‐BPLC template and L‐BPLC with a maximal total reflectance of 25% or a blue color BPLC achieved in BPI, the proposed multi‐layer BPLC film consisting of two BPLC templates with opposite handedness in BPII demonstrates a distinguished advantage of hyper‐reflectivity in the visible range. It can be seen that the reflection spectrum of multi‐layer BPLC films refilled by achiral nematic LC HTG135200‐100 is centered at 650 nm, 550 nm, and 440 nm, with a maximal reflectance of 89%, 82%, and 68% (3.6 times, 3.3 times, and 2.7 times compared to recently demonstrated results), respectively. The insets of Figure a–c show photos of multi‐layer BPLC films taken under a fluorescent lamp, indicating the full‐color, hyper‐reflective film fabricated by our method.…”

“…Hyper‐reflectivities of 89%, 82%, and 68% in the red, green, and blue reflection color regions were achieved by refilling the multi‐layer blue phase liquid crystal films with free‐standing porous polymer network with an achiral nematic liquid crystal. The newly developed multi‐layer BPLC film substantially improved the overall reflection efficiency by as much as 3.6, 3.3, and 2.7 times (in red, green, and blue, respectively), compared to previous results . The reflectance switching of the film was achieved by unwinding the helical structure of the blue phase in an electric field, where highest reflectances of 94%, 86%, and 72% were achieved in the red, green, and blue color regions, respectively, under an electric field of 1 V µm −1 .…”

“…The transfer of the orientational order of the blue phase to the surface of the polymer matrix and the resulting surface anchoring were numerically modeled . Based on the BPLC template, Guo et al reported a double‐layer BPLC film with a segregation of the left‐handed (LH) and right‐handed (RH) domains across the LC film to reflect both left‐ and right‐circularly polarized light . In Guo's paper, two kinds of double‐layer structures were demonstrated: one was fabricated using a R‐BPLC template and a L‐BPLC template, with a reflectance of 25%; another was fabricated using a R‐BPLC template and a pure L‐CLC, with a reflectance of 36%.…”

3D Chiral Photonic Nanostructures Based on Blue‐Phase Liquid Crystals

“…The phase behavior of the resulting BPLCs can be efficiently manipulated by trans – cis photoisomerization of the azobenzene dopant. [ 157–159 ] Lin et al prepared a chiral azobenzene molecular switch and incorporated it into a BP host to realize the light‐driven shifting of photonic bandgap ( Figure ). [ 160 ] The resultant BP materials initially exhibited a blue reflection color and simple cubic BP II nanostructures.…”

Stabilization and optical switching of liquid crystal blue phase doped with azobenzene-based bent-shaped hydrogen-bonded assemblies

“…46,47 We note that this is different from that of the BP-LC system doped with chiral dopants with azobenzene group. 35,48,49 When irradiated by visible light, the reection band could completely restore since the cis-isomer turns back to the trans conguration. This demonstrates that the phototuning process is reversible by UV/Vis light.…”