최석원 교수

The relationship between material parameters of host nematic liquid crystals (LCs) and Kerr constant of their nanostructured chiral LC composites was investigated. We made certain that the Kerr constant of nanostrutured chiral LC composites was closely related to the parameters of their host LCs, such as value of the difference of refractive index (Δn), the dielectric anisotropy (Δε), and bend to splay elastic constant ratio (K33∕K11).

Imperative irradiation: A large enantiomeric excess in a liquid-crystal phase can be induced by circularly polarized light (CPL) as an external stimulus, and an imbalance in the two chiral domains becomes remarkable in the BX phase (see pictures), which is similar to the B4 phase made up by classical bent-core mesogens.

We investigated the liquid crystalline blue phase I (BP I) observed for a nematogenic achiral bent-core molecule doped with a small percentage of a chiral additive with a high twisting power. We also observed the electro-optical performance of BP I by incorporating in-plane electric field geometry.

A lasing peak shift of more than 100 nm is realized due to the large shift of a photonic bandgap of a liquid-crystalline blue phase.

In this article, we will review the phenomena on circularly-polarized-light (CPL)-induced chirality in polymeric systems with photochromophores in their side-chain or main-chain. In the side-chain polymeric systems, the photoinduced chirality arises from superstructural chirality, i.e., helix structure, via aggregating of achiral azobenzene molecules in side chains. On the other hand, in the main-chain polymeric system, the macroscopically induced chirality can originate from individual chiralit

We investigated the relationship between the elastic constants of host nematic liquid crystals (NLCs) and the thermal stability of their liquid crystalline blue phase I (BPI). By adding bent-core molecules to a conventional NLC, we could gradually increase (decrease) the elastic constant K11 (K33). We confirmed experimentally that the thermal stability of BPI strongly depends on the ratio of the elastic constants K11 and K33 of the host NLCs; the stability increases with decreasing K33/K11 parti

A well-aligned dye-doped blue phase II laser shows tunable emission wavelength and much lower emission threshold energy.

The temperature ranges where a pure simple-cubic blue phase (BPII) emerges are quite narrow compared to the body-centered-cubic BP (BPI) such that the polymer stabilization of BPII is much more difficult. Hence, a polymer-stabilized BPII possessing a wide temperature range has been scarcely reported. Here, we fabricate a polymer-stabilized BPII over a temperature range of 50 °C including room temperature. The fabricated polymer-stabilized BPII is confirmed via polarized optical microscopy, Bragg

Going bananas: In a twisted geometry, an extrinsically chiral supermolecular structure was obtained in the calamitic phase. Upon cooling down to form the Bx phase, imbalanced growth of an intrinsic preferential chiral structure was attained. The preferential chiral handedness of the banana mesophase can be also controlled by the handedness of the twisted configuration.

Abstract A simple methodology is developed to realize chiroptical function induced through superstructural chirality of a matrix of helical nanofilaments formed by achiral molecules. In this work, circularly polarized luminescence is demonstrated in nanosegregated mesophase comprising only achiral molecules. An achiral molecular mixture of a bent‐core host and a rod‐like guest blended with a fluorescent dye is prepared. Circularly polarized luminescence confirms that the chiral superstructure co

A thermodynamically stable blue phase II (BPII) has been prepared, and its electrooptical (EO) performance has been evaluated in a host system of a conventional rodlike nematogen mixed with a bent-core molecule. For the mixed system presented, the widest temperature range of BPII stability, during cooling/heating, was >6 °C. This range is much wider than those of conventional nematogens blended with chiral dopants. EO observations show that the BPII produced exhibited stable EO performance based

Second-harmonic generation (SHG) has been observed as functions of temperature, electric field and incidence angle in the liquid crystal phases of the achiral bent-shaped molecules with octyloxy end chains (P-8-O-PIMB). In the highest temperature B 2 phase, the SHG for oblique incidence started to appear at an electric field when the texture change due to the electric-field-induced molecular and dipolar reorientations occured. The SHG interferometry clearly indicated the reversal of polarization

Herein, an epoch-making method based on bottom-up templating is proposed for the fabrication of a chiral nanoporous film that provides a chiral environment in which to confine nematic liquid crystals. A helical nanofilamental network of bent-core molecules was utilized as a three-dimensional mold, and thus the fabricated chiral nanoporous film has an inverse nanohelical structure. The presence of a chiral superstructure was confirmed by the observation of circular dichroism signals. Upon refilli

Abstract Structure and switching behavior were studied in liquid crystals consisting of bent-shaped molecules with the linkage of an alkylene spacer, m(O)AMnAM(O)m, where m and n are carbon numbers of end and spacer chains, respectively. All the compounds exhibit a fan-shaped texture without a fringe structure in their smectic phase, different from the texture of conventional bent (banana)-shaped liquid crystals. In 12AM5AM12, two switching current peaks indicating the antiferroelectric phase we

Photoinduced circular anisotropy has been demonstrated in thin films of a main-chain polymeric liquid crystal (PLC) system doped with photochromic W-shaped molecules containing two azobenzene groups by irradiating with circularly polarized light (CPL). Reversible photoinduced circular dichroism (CD) was observed with sign relevant to the handedness of the CPL. The experimentally observed CD spectra were analyzed using the DeVoe polarizability model associated with the coupled oscillator method.