Yasushi Okamoto

Bio: Yasushi Okamoto is an academic researcher from Denso. The author has contributed to research in topics: Epoxy & Adhesive. The author has an hindex of 3, co-authored 11 publications receiving 34 citations.

Heterogeneous dynamics in the curing process of epoxy resins.

Abstract: Epoxy resin is indispensable for modern industry because of its excellent mechanical properties, chemical resistance, and excellent moldability. To date, various methods have been used to investigate the physical properties of the cured product and the kinetics of the curing process, but its microscopic dynamics have been insufficiently studied. In this study, the microscopic dynamics in the curing process of a catalytic epoxy resin were investigated under different temperature conditions utilizing X-ray photon correlation spectroscopy. Our results revealed that the temperature conditions greatly affected the dynamical heterogeneity and cross-linking density of the cured materials. An overview of the microscopic mechanism of the curing process was clearly presented through comparison with the measurement results of other methods, such as 1H-pulse nuclear magnetic resonance spectroscopy. The quantification of such heterogeneous dynamics is particularly useful for optimizing the curing conditions of various materials to improve their physical properties.

“Buried” nano-structure and molecular aggregation state in ordered heterojunction poly(3-hexylthiophene)-based photovoltaics

Abstract: The morphology of ordered heterojunction organic photovoltaics (OHJ-OPVs) interfaces was evaluated using synchrotron radiation small angle X-ray scattering and grazing incidence X-ray diffraction. [6,6']-phenyl C61-butyric acid methyl ester (PCBM) was deposited on the line/space patterned poly(3-hexylthiophene-2,5-diyl) (P3HT) thin film fabricated by nano-imprinting. After deposition of the PCBM film, the P3HT thin film retained the rectangular edge features of the imprinted mold, with some Gaussian broadening due to interdiffusion and partial phase mixing at the P3HT/PCBM interface. The P3HT main chains were oriented vertically in the nano-imprinted line pattern and showed π–π stacking along the line direction. PCBM nano-crystals exist throughout the OHJ-OPV thin film.

Adhering method of polyacetal resin molded product, polyacetal resin molded product, and composite molded product

Abstract: PROBLEM TO BE SOLVED: To provide an adhering method of a polyacetal resin molded product for expressing an excellent adhesiveness while maintaining the original property of the polyacetal resin. SOLUTION: The method for adhering the polyacetal resin molded product to an adherend by an adhesive comprises: a step of treating the surface of the polyacetal resin molded product to generate hydroxyl groups on the surface of the polyacetal resin molded product and to react the generated hydroxyl groups with an organosilicone compound; and a step of expressing the adhesiveness by an interaction between the functional groups of the organosilicone compound reacted with the hydroxyl groups generated on the surface of the polyacetal resin molded product and the functional groups of the adhesive. COPYRIGHT: (C)2009,JPO&INPIT

Resin bonding method

Abstract: PROBLEM TO BE SOLVED: To provide a resin bonding method for bonding a polyester resin to an epoxy-based adhesive, having excellent adhesiveness. SOLUTION: The method is for bonding a polyester resin 2 to an epoxy-based adhesive 3. The epoxy-based adhesive 3 is bonded to an adhesive surface 202 after surface treatment for providing the surface 201 of the polyester resin 2 with an oxygen-containing functional group. The oxygen-containing functional group is a hydroxy group, a carbonyl group or a carboxy group. The method is for bonding the polyester resin 2 after annealing treatment to the epoxy-based adhesive 3. The oxygen-containing functional group is formed in an area in thickness of 3-10 nm from the surface 201 of the polyester resin 2. COPYRIGHT: (C)2008,JPO&INPIT

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

Abstract: The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ev...

Anti-fouling behavior of polymer brush immobilized surfaces

Abstract: Nature-inspired material design concepts and recent progress on anti-fouling polymer materials are reviewed, and our recent researches on anti-fouling studies with polymer brushes are summarized. Zwitterionic polyelectrolyte brush immobilized surfaces represent significant anti-fouling for bio-macromolecules, oil foulants, marine fouling organisms and pipeline foulants. The anti-fouling mechanism was considered on the basis of the wetting, lubrication, hydrated chain dimension and hydrogen-bonding structure of hydrated water in the polyelectrolyte brushes.

Layer‐by‐Layer Processed Organic Solar Cells

Abstract: Layer-by-layer (LL) processes, i.e., sequential deposition of different active layers, are widely used in the fabrication of organic solar cells (OSCs). Recently, LL vacuum deposition and LL solution processes have attracted considerable attention. LL processing presents some advantages over the blend method: a) donor and acceptor layers can be easily and independently controlled and optimized; b) the charge carriers dissociated from excitons at the donor–acceptor interface are confined to each phase, so bimolecular recombination losses can be reduced; c) bilayer geometries enable an easier way for understanding the physical processes taking place at the donor–acceptor interface; d) desired vertical phase separation for charge extraction can be obtained through changing the sequence of donor and acceptor deposition. This report summarizes the recent developments of LL processed OSCs. The remaining problems and challenges, and the key research direction in near future are discussed.

Novel Fluorinated Polymers Containing Short Perfluorobutyl Side Chains and Their Super Wetting Performance on Diverse Substrates

Abstract: Because the emission of perfluorooctanoic acid (PFOA) was completely prohibited in 2015, the widely used poly- and perfluoroalkyl substances with long perfluoroalkyl groups must be substituted by environmentally friendly alternatives. In this study, one kind of potential alternative (i.e., fluorinated polymers with short perfluorobutyl side chains) has been synthesized from the prepared monomers {i.e., (perfluorobutyl)ethyl acrylate (C4A), (perfluorobutyl)ethyl methacrylate (C4MA), 2-[[[[2-(perfluorobutyl)]sulfonyl]methyl]amino]ethyl acrylate (C4SA), and methacrylate (C4SMA)}, and the microstructure, super wetting performance, and applications of the synthesized fluorinated polymers were systematically investigated. The thermal and crystallization behaviors of the fluoropolymer films were characterized by differential scanning calorimetry and wide-angle X-ray diffraction analysis, respectively. Dynamic water-repellent models were constructed. The stable low surface energy and dynamic water- and oil-repell...