The development of stimuli-responsive polymers is among the key goals of modern materials science. The structure and properties of such switchable materials can be designed to be controlled via various stimuli, among which light is frequently the most powerful trigger. Light is a gentle energy source that can target materials remotely, and with extremely high spatial and temporal resolution easily and cheaply. Reversible light-control over molecular mechanical properties in particular has in recent years attracted great interest due to potential applications as optical-to-mechanical conversion actuators and 'devices', enabling 'molecular robotic machines'. In this review, some recent examples and emerging trends in this exciting field of research are highlighted, covering a wide variety of polymer hosts that contain azobenzene photo-reversible switches. It is hoped that this review will help stimulate more interest towards the development of light-reversible materials for energy harvesting and conversion, and their successful incorporation into a wide variety of current and future high-tech applications in devices.

Liquid crystals are 2D patterned with nonpolarized light by a new dye-free photoalignment method.

Control over the orientation of metal nanorods is important for both fundamental and applied research. We show that gold nanorods (GNRs) can be aligned in a single direction by adsorbing positively charged GNRs onto a double-strand DNA-grafted substrate through electrostatic interaction. The ordered structure can be optimized by controlling the density of the positive charges on the surface of the GNRs. We found, in agreement with the results of theoretical simulation, that the resultant structure exhibits plasmonic properties that are dependent on the GNR orientation relative to the direction of an oscillating electric field. Our approach provides new insights into the polymer-assisted self-assembly of rod-shaped nanoparticles utilizing electrostatic interactions.

We investigate the liquid crystal (LC) phase behaviors of the sodium cholate stabilized single-walled carbon nanotube (SWCNT) aqueous dispersions with different SWCNT aspect ratios. The isotropic-to-nematic phase transition occurs at a lower concentration for the SWCNT dispersion with larger aspect ratio, which is expected by the Onsager theory. The well-aligned film is successfully fabricated from the dispersion with the a higher SWCNT aspect ratio by the simple blade coating. We also prepare the SWCNT dispersions with different surfactants, sodium deoxycholate and sodium taurodeoxycholate, changing the surface condition of SWCNTs, which may affect the LC transition concentrations.

Controlling the alignment of single-walled carbon nanotubes (SWCNTs) on the macroscopic scale is critical for practical applications because SWCNTs are extremely anisotropic materials. One efficient technique is to create an effective SWCNT dispersion, which shows a liquid crystal (LC) phase. A strong acid treatment can realize SWCNT liquid crystalline dispersions. However, strong acids pose a substantial safety risk, which renders the process unfit for mass production. Herein, an isolated SWCNT dispersion displaying an LC behavior is prepared using sodium cholate without an acid treatment, and its phase transition behaviors are systematically investigated across the isotropic to biphasic to nematic phases. As the SWCNT concentration increases, the dispersion undergoes an isotropic-to-nematic phase transition in which the spindle-shaped LC droplets, or the so-called tactoids, and the Schlieren textures can be observed in the intermediate biphasic state and the nematic phase, respectively. The arrangements of SWCNTs in the tactoids and the Schlieren structures are directly investigated by polarized optical microscopy. The clear LC behaviors of the CNT dispersion suggest that the CNT orientations can be controlled by the normal surfactant-assisted method, which is a crucial advantage for the liquid-phase processing of CNT fibers and films.

Tunable photonic crystals exhibiting optical properties that respond reversibly to external stimuli have been developed using liquid crystal networks (LCNs) and liquid crystal elastomers (LCEs).

Adhesion technology, in which materials are bonded together to create an integrated material, is widely used in a range of household, commercial, and industrial applications. [1] In recent years, adhesives have received more attention from the viewpoint of energy consumption. In the automobile industry, reducing vehicle mass is a key factor regarding the demand for improving energy efficiency. Therefore, adhesives are becoming more important and more in demand owing to their availability to bond different materials that cannot be bonded through typical mechanical methods. [2] Among these demands for new adhesion technologies, sustainability through material lifecycle has also been recognized as an important factor. [3] Dismantlable adhesives that have been developed to meet these requirements exhibit sufficient adhesion strength during use and can be easily separated by external stimuli when the material in question needs to be recycled or repaired. [4][5][6] Various types of dismantlable adhesives have been developed that reduce the adhesive force by utilizing stimuli such as heating, [7][8][9][10][11][12] light irradiation, [13][14][15][16][17][18][19][20][21] electric fields, [22] magnetic fields, [23] and chemical treatments. [24][25][26] These dismantlable adhesives maintain the changed state caused by applying the stimulus; thus, there is no regain in their original adhesive strength even in the absence of the stimulation. This feature enables easy separation without the need for continuous stimulation. Despite the recent progress on these functional adhesives, neither is currently universally accepted in dismantling systems. [6] One considerable reason of this circumstance is that the dismantling mechanisms are limited to changes in bulk state, such as controlling the cohesiveness of the adhesives. This limitation requires large amounts of trigger materials, such as stimulusresponsive molecules, to dismantle these adhesives by changing their entire state. Therefore, the development to achieve both sufficient adhesion strength and an efficient dismantling system is difficult because the overall condition of adhesives needs to be involved.The surface treatment of adherends also plays a critical role in ensuring sufficient adhesion strength; altering the surface treatment is more efficient than changes in bulk state. [27] A typical example of surface treatment is a coating process applied to the base materials, which is known as a primer treatment. This has been conventionally used as a method to improve adhesion strength. [28] For example, phosphoric acid primers are used to improve adhesion between resin cements and zirconia ceramics, for which it is normally difficult to achieve suitable adhesion. [29,30] Organosilane compounds are used as coating agents to improve the adhesion strength between metal and

Controlled and uniform molecular alignment can provide and enhance functionality in polymer films. We first report that masked photopolymerization with non-polarized light enables direct and precise control of molecular alignment without using a conventional molecular alignment layer. The photopolymerization of a mixture composed of an optically anisotropic acrylate monomer and an isotropic dimethacrylate crosslinker induces either unidirectional or complex molecular alignment, depending upon the shape of the photomask. Such molecular alignments are successfully achieved by shear stress arising from molecular diffusion, even when the photopolymerization is carried out at isotropic temperatures of both the monomer mixture and the obtained polymers.