Optical Switching between Liquid-Crystalline Assemblies with Different Structural Symmetries and Molecular Orders

Abstract

Optical switching between one-dimensionally ordered layered smectic C (SmC) and three-dimensionally periodic bicontinuous cubic (Cubbi) liquid-crystalline (LC) phases is a fascinating challenge because of the dramatic changes of structural symmetries and orders as well as physical properties. In this work, we have developed a new light-driven Cubbi phase system consisting of 4′-n-hexadecyloxy-3′-cyanobiphenyl-4-carboxylic acid (ACBC-16) and a structurally analogous azo compound (Azo-2). The employment of the CN side-group in the host compound brought about outstanding responsiveness under ultraviolet (UV) light in the mixtures containing 11 and 19 mol % Azo-2, leading to a UV response time of ∼5 s and excellent repeatability of on-off switching for the conversion between the two LC phases. The modification also enabled us to quantitatively analyze the mechanism of the light-induced transformation between the two LC phases. The evaluation revealed that the presence of ∼4% of bent molecules in the system under UV light destabilizes the SmC layered structure originally constructed by rod-shaped molecules, causing formation of the Cubbi phase at temperatures 10–35 K below the temperature range of the thermally-stable Cubbi phase.

Photohardenable Pressure-Sensitive Adhesives using Poly(methyl methacrylate) containing Liquid Crystal Plasticizers

“…So far, the photochemical phase transition of azobenzene compounds was extensively studied for a variety of liquid-crystalline phases. − Photochemical nematic–isotropic phase transition observed also for PP 5 is a common example. , In this study, photochemical smectic E–isotropic phase transition observed for PP 50 was for the first time confirmed to the best of our knowledge. More interestingly, the photochemical phase transition could be observed even in the crystalline phase of BMAB (PP 100 ), namely the crystal–liquid phase transition.…”

Structural relationships for the design of responsive azobenzene-based lyotropic liquid crystals

“…A recent study by Nagai et al demonstrated the feasibility of such changes using an azobenzene photoswitch. 32 Their study found a ternary thermotropic system in which photo-isomerization was shown to induce transition between smectic C (SmC) and bicontinuous cubic (Ia3d) spacegroups, however, this ternary system has a working temperature range around 400 K. Room temperature reproduction of such drastic space group changes therefore remains a challenge. Since lyotropic systems offer a facile route to reaching analogous LC phases, the study of lyotropic systems and their behaviour may offer a way to achieve this goal.…”

Nanoarchitectonics from Atom to Life

“…Kutsumizu and co-workers demonstrated optical switching of liquid crystalline phases between one-dimensionally ordered layered smectic C phase and three-dimensionally periodic bicontinuous cubic phase based on well-considered molecular designs and mixing ratio regulations of 4'-n-hexadecyloxy-3'-cyanobiphenyl-4-carboxylic acid and its azobenzene analogues. [51] The presence of appropriate amounts of bent species within liquid crystalline of rod-shaped molecules induced transition into three-dimensional phase. Nanoarchitectonics design with integration of functional materials and stimuli-responsive structures are widely researched.…”