Motonori Komura

Synthesis and self-assembly of phthalocyanine-tethered block copolymers

A series of novel phthalocyanine (Pc)-tethered block copolymers, Pc-poly(methyl methacrylate)-block-polystyrene (Pc-PMMA-b-PS), with various molecular weights (number average molecular weight mass = 41, 66, 86 kg mol−1), were prepared by atom transfer radical polymerization and click chemistry. The structurally related Pc-tethered homopolymer, Pc-PMMA was also synthesized for comparison. Pc-PMMA forms homogeneous polymer films containing π-assemblies of the terminal Pc groups, whereas Pc-PMMA-b-PS self-assembles into a cylindrical morphology in which the Pc units show π–π interactions inside the confined PMMA cylinders. Such polymer designs have potential applications in optoelectronic devices.

Chemically directed self-assembly of perpendicularly aligned cylinders by a liquid crystalline block copolymer

Chemical epitaxy with a density multiplication process was applied to the perpendicularly oriented hexagonal cylinder nanostructure of liquid crystalline block copolymer (PEO-b-PMA(Az)) thin film through thermally induced microphase separation by using a newly designed PMA(Az)24 brush. The hexagonal lattice orientation with 1.9 tera-cylinders per inch2 was laterally controlled for long-range-ordered direct self-assembly. Furthermore, the direct pattern-transfer of the assembled structure to an Au nanodot array was demonstrated by doping of HAuCl4 selectively into the PEO cylindrical microdomains and then vacuum ultraviolet light irradiation to cause polymer etching and reduction of the Au ions.

Site-Selective Self-Assembly of Fullerene Nanoparticles on Amphiphilic Block Copolymer Thin Film from Water Suspension

We present a simple and versatile approach to selectively deposit fullerene nanoparticles on a nano scale ordered self-assembled thin film of amphiphilic poly(ethylene oxide)-block-polymethacrylate with azobenzene mesogen [PEO-b-PMA(Az)]. Fullerene nanoparticles were fabricated by the reprecipitation method, and the surface morphology of the block copolymer film deposited with C60 nanoparticles was characterized by atomic force microscopy (AFM). The fabricated ordered C60 nanoparticles may lead to a promising route for fabricating electronic or photocatalytic devices.

Pulsed NMR Studies on Long-Term Crystallization Behavior and Melting Process of Natural Rubber under Elongation

Abstract Long-term crystallization and melting process of natural rubber under elongation was investigated by measuring spin-spin relaxation time T2 by pulsed nuclear magnetic resonance (NMR). We examined the dependence of the both processes on extension ratio, crystallization temperature and crosslink density. It was found that the crystallization of natural rubber continued over three months even at 10 °C. According to the two-step melting process found for the first time under elongation, we proposed a model that crystalline part of natural rubber under large elongation is composed of two kinds of crystallites from highly extended and loose chains. The situation is caused by the microscopic distribution of extension ratio of the chains between crosslink points.

Hexagonally Arrayed 17 nm Interpenetrating and Continuous Biphasic Structure via Block-Copolymer-Templating Process

Biphasic and interpenetrating continuous membranes with precisely controlled two-dimensional (2D)-hexagonal nanoperiodicity were fabricated using amphiphilic block copolymer poly(ethylene oxide)-b-polymethacrylate with azobenzene mesogen units in the side chain [PEOm-b-PMA(Az)n]. On a silica (SiO2) nanodot array templated from the block copolymer membrane, the next phase, such as titanium dioxide (TiO2), or gold (Au), was coated. Herein, the surface modification of the transferred SiO2 nanodot array was crucial to obtaining the interpenetration of the precursor of TiO2 and its continuous contact. The typical size of the hexagonal array (d) and the center-to-center distance (D) of the SiO2 nanodots were (d, D) = (17 nm, 27 nm) and (d, D) = (22 nm, 51 nm), respectively. The interpenetrating and continuous biphasic structure will provide a promising approach to multiferroic materials, interpenetrative heterojunction for solar cells, new integrated catalysts, and so forth.

Atomic step-and-terrace surface of polyimide sheet for advanced polymer substrate engineering

Typical thermostable and flexible polyimide polymers exhibit many excellent properties such as strong mechanical and chemical resistance. However, in contrast to single-crystal substrates like silicon or sapphire, polymers mostly display disordered and rough surfaces, which may result in instability and degradation of the interfaces between thin films and polymer substrates. As a step toward the development of next-generation polymer substrates, we here report single-atom-layer imprinting onto the polyimide sheets, resulting in an ultrasmooth 0.3 nm high atomic step-and-terrace surface on the polyimides. The ultrasmooth polymer substrates are expected to be applied to the fabrication of nanostructures such as superlattices, nanowires, or quantum dots in nanoscale-controlled electronic devices. We fabricate smooth and atomically stepped indium tin oxide transparent conducting oxide thin films on the imprinted polyimide sheets for future use in organic-based optoelectronic devices processed with nanoscale precision. Furthermore, toward 2D polymer substrate nanoengineering, we demonstrate nanoscale letter writing on the atomic step-and-terrace polyimide surface via atomic force microscopy probe scratching.

Slowing the translocation of single-stranded DNA by using nano-cylindrical passage self-assembled by amphiphilic block copolymers

We report a novel approach to slow the translocation of single-stranded DNA (ssDNA) by employing polyethylene oxide (PEO) filled nano-cylindrical domains as transportation channels. DNA strands were demonstrated to electrophoretically translocate through PEO filled cylindrical domains with diameters of 2 and 9 nm, which were self-assembled by amphiphilic liquid crystalline block copolymers. The average translocation rate of ssDNA strands was effectively reduced to an order of 10 μs per nucleotide, which was 1-2 orders slower than that attained by utilizing conventional solid-state nanopore devices.

Hexagonally Arranged Nanopore Film Fabricated via Selective Etching by 172-nm Vacuum Ultraviolet Light Irradiation

Abstract Highly ordered nanopore arrays were successfully fabricated using poly(ethylene oxide) (PEO) and polymethacrylate with azobenzene mesogen in side chains [PMA(Az)] block copolymer film based on irradiation of 172-nm vacuum ultraviolet (VUV) light. The block copolymer forms a highly ordered microphase-separated film with perpendicularly oriented PEO cylinders just by thermal annealing through a self-assembling process. We found that the etching rate of the PEO homopolymer was much higher than that of the PMA(Az) homopolymer at a chamber pressure of 102 Pa of atmosphere under VUV irradiation. The etching rate of the PEO component in the two systems of microphase separation and macrophase separation of the homopolymer blend crucially depended on the feature size of phase separation. In the PEO selective etching process of the block copolymer film, the water-contact angle of the film dramatically increased due to elimination of hydrophilic PEO. The resulting nanopore array film will be useful for low-density target materials.

Nano-Level Surface Processing of Fine Particles by Cavitation to Improve the Photocatalytic Properties of Titanium Oxide

Titanium oxide is known as a photocatalytic material that promotes the generation of hydrogen and oxygen from water by sunlight irradiation. In the present study, titanium oxide particles were treated by water jet cavitation generated using an ejector nozzle. Sub-stream suction occurs in small-sized high-pressure ejector nozzles because of the dynamic high pressure. The water containing titanium oxide powder or a mixed powder of titanium oxide and platinum enters the high-pressure water flow as a sub-stream. In the ejector nozzle, generation, growth, and collapse of cavitation are repeated with the particles of titanium oxide and platinum. Because the cavitation has an extremely high collapse pressure, the surface of the titanium oxide particles is processed by the microjets of cavitation in a so-called reactor comprising the ejector nozzle. The titanium oxide particles subjected to ejector cavitation (EC) processing were investigated for improvements to their photocatalytic properties under ultraviolet irradiation. It was found that noted that nano-level roughness is formed by EC processing. The TiO2 particles or TiO2 particles supported by Pt particles as a co- catalyst containing water were introduced into a vacuum chamber and the gases such as hydrogen and oxygen from the particle surfaces were measured by quadrupole mass spectrometry under ultraviolet irradiation. The EC processing was found to increase the amount of gases generated, including hydrogen and oxygen. Moreover, the amount of hydrogen in particular increases remarkably when both EC processing and support of platinum as a co-catalyst are used. It was also found that the titanium TiO2 particles were supporting minute platinum particles that detached from the original Pt particles during EC processing.