Joji Ohshita’s research while affiliated with Hiroshima University and other places

Aiming to develop antifogging materials with enhanced antifogging properties and scratch resistance, polysilsesquioxane films containing quaternary ammonium groups were prepared via a sol–gel reaction and quaternization. Owing to their high water uptake, scratch hardness, and transparency, the prepared quaternary ammonium-functionalized polysilsesquioxane films are promising for application in antifogging coatings.

Overcrowded bistricyclic aromatic enes (BAEs) have several conformational isomers, including twisted and anti-folded conformers. These compounds change color depending on their conformation because each isomer exhibits distinct absorption bands. In this study, we introduced several heteroatoms such as boron and silicon into BAEs to control the energy difference between the twisted and anti-folded conformers, thereby achieving chromic properties. The heteroatom-containing BAEs showed absorption bands attributable to both twisted and anti-folded conformers, suggesting the coexistence of these conformers in solution. Although the solution appeared bluish, yellowish crystals were obtained by recrystallization. Single-crystal X-ray diffraction analysis confirmed that the yellowish crystals existed in the anti-folded conformation. The color of these crystals changed from yellowish to bluish upon heating and grinding, demonstrating thermochromism and mechanochromism. In addition, when cyanide ions were added to the BAE solution, the color changed from bluish to colorless, indicating the chemochromic properties of the BAEs.

The twisted conformer of bistricyclic aromatic enes (BAEs) has a small HOMO–LUMO gap owing to the twisted double bond. In this study, we synthesized diphenoquinones fused with thiophene rings as...

Heteroatoms such as boron significantly alter the photophysical properties of π-conjugated materials, making heteroatom-containing π-conjugated materials widely used in fields such as photoluminescent materials. This paper introduces recent developments and future prospects of optoelectronic materials based on triarylborane structures, particularly photoluminescent materials, which have seen remarkable advancements in recent years.

Heat insulators are key materials for efficient energy use and reduction of CO 2 emissions. Recently, we examined cross-linked polymethylsilsesquioxane (MSQ) for use as the basic structure of heat-resistant insulation materials. In this study, we prepared MSQs with different cross-linking units and examined the effects of their structures on the heat resistance and heat insulation properties. Among those, MSQ linked by diethynylbenzene had sufficiently low thermal diffusivity and moderately high heat resistance. We also showed their structure–thermal property relationships. Although other influencing factors could exist, the rigidity, π‒π interactions, and bulkiness of the cross-linking units were found to predominantly influence the thermal properties. These findings will lead to new molecular designs for polysilsesquioxane (PSQ)-based heat-resistant heat insulators with high performance.

Boron-containing antiaromatics, such as diborinines and boroles, have sparked interest in materials chemists owing to their exciting optical properties and high Lewis acidity. In this study, we synthesized donor–acceptor (D–A) type diborinines fused with thiophene rings by introducing electron-donating amino-substituted aryl groups onto boron and elucidated their properties. The D–A type dithienodiborinines exhibited long-wavelength absorption arising from their D–A interactions and antiaromaticity. In addition, their fluorescence intensity increased under oxygen-free conditions, indicating thermally activated delayed fluorescence.

It is known that X‐ray CT of organic polymer materials usually provides low‐contrast images because of the low X‐ray absorption of these materials. In this paper, we describe a new method to enhance the contrast of X‐ray CT images of organic polymer materials. We demonstrate that gamma‐ray irradiation of poly (ethylene terephthalate) (PET) fibers in dichloromethane containing 2‐bromoethyl methacrylate, 2‐chloroethyl methacrylate, or 4‐bromostyrene results in the grafting of halogen‐containing oligomeric chains onto the PET fibers. Focused ion beam scanning electron microscopy (FIB‐SEM) and time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) analyses revealed a homogeneous distribution of bromine atoms within the 2‐bromoethyl methacrylate‐modified PET fibers, not only on the surface. This uniform incorporation translated to a significant improvement in X‐ray CT image contrast compared with pristine fibers. Similar treatment of polypropylene pellets also enhanced the contrast of their X‐ray CT images. This is a new simple and effective method to enhance the X‐ray CT image contrast and potentially applicable to various polymer materials including polymer composites and porous polymer materials, readily allowing the observation of their 3D microstructures finely.

Group 14 metalloles have attracted much attention as core structures of conjugated functional materials. In this work, we prepared dithieno[3,2-b:4,5-c’]germole as a new unsymmetrically condensed dithienogermole and benzo[4,5]thieno[2,3-c]germole as the benzene-condensed analog. The electronic states and properties of these unsymmetrically condensed germoles are discussed on the basis of the results of optical and electrochemical measurements with the help of quantum chemistry calculations on the simplified model compounds. The Stille cross-coupling reactions of bromodithieno[3,2-b:4,5-c’]germole with di(stannylthienyl)- and di(stannylthiazolyl)benzothiadiazole provided conjugated donor–acceptor compounds that exhibited clear solvatochromic behavior in the photoluminescence spectra, indicating the potential application of the dithieno[3,2-b:4,5-c’]germole unit as an electron donor in donor–acceptor systems.

The automotive industry is rapidly advancing toward the electrification of vehicles. Battery electric vehicles present unique challenges in heat and noise control due to the absence of an internal combustion engine. These challenges arise from the stringent operating temperature requirements of batteries and the distinct characteristics of their power sources, such as differences in rpm and mounting positions compared to traditional engines. To address these issues, porous sound-absorbing materials and porous insulation materials are commonly employed. Conversely, there is an increasing demand for materials that are both lightweight and compact yet capable of providing excellent sound absorption and thermal insulation. Although porous sound absorbers and insulators are similar, they differ in the microstructure required to achieve high performance, specifically in the size and connectivity of their fluid phases. This increases the challenge of integrating superior sound absorption and insulation properties within the same material. In this study, computational microstructure modeling was employed to develop a non-woven fabric composed of flattened ellipsoidal particles with nanoporosity. This innovative material demonstrates exceptional thermal insulation and sound absorption characteristics attributable to its nanoporosity and high tortuosity.