Junpei Miyake

Highly luminescent BODIPY-based organoboron polymer exhibiting supramolecular self-assemble structure.

A novel class of rod-coil type-organoboron polymers with p-phenylene-ethynylene as the rod segment and long alkyl chain (decyl group) as coil segment has been prepared from a Sonogashira-Hagihara coupling reaction of a BODIPY-based monomer having bis-iodophenyl and decyl groups with diyne monomers, 1,4-diethynylbenzene (a), 1,4-diethynyl-2,5-bis(trifluoromethyl)benzene (b), and 2,7-diethynyl-9,9-dihexyl-9H-fluorene (c). The characterization by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the strong tendency of the obtained polymers, 2a, 2b, and 2c, to self-assemble into particles in solution and as-casted films on a micron-nm scale. Especially, 2a showed the presence of nm-sized particles and micron-sized fiber-like structures formed by aggregation of each particle. Further, in CHCl3, the gelation of 2a by three-dimensional aggregation of each fiber was observed at room temperature after 24 h. Their luminescent properties showed high energy transfer efficiency from pi-conjugated polymer linkers to BODIPY moieties (PhiF > 71%).

Anion Conductive Aromatic Block Copolymers Containing Diphenyl Ether or Sulfide Groups for Application to Alkaline Fuel Cells

A novel series of aromatic block copolymers composed of fluorinated phenylene and biphenylene groups and diphenyl ether (QPE-bl-5) or diphenyl sulfide (QPE-bl-6) groups as a scaffold for quaternized ammonium groups is reported. The block copolymers were synthesized via aromatic nucleophilic substitution polycondensation, chloromethylation, quaternization, and ion exchange reactions. The block copolymers were soluble in organic solvents and provided thin and bendable membranes by solution casting. The membranes exhibited well-developed phase-separated morphology based on the hydrophilic/hydrophobic block copolymer structure. The membranes exhibited mechanical stability as confirmed by DMA (dynamic mechanical analyses) and low gas and hydrazine permeability. The QPE-bl-5 membrane with the highest ion exchange capacity (IEC = 2.1 mequiv g(-1)) exhibited high hydroxide ion conductivity (62 mS cm(-1)) in water at 80 °C. A noble metal-free fuel cell was fabricated with the QPE-bl-5 as the membrane and electrode binder. The fuel cell operated with hydrazine as a fuel exhibited a maximum power density of 176 mW cm(-2) at a current density of 451 mA cm(-2).

Anion exchange membranes composed of perfluoroalkylene chains and ammonium-functionalized oligophenylenes

A novel series of ammonium-containing copolymers (QPAFs) were synthesized as anion exchange membranes for alkaline fuel cell applications. The precursor copolymers (Mw = 28.3–90.1 kDa) composed of perfluoroalkylene and phenylene groups were obtained by a nickel promoted polycondensation reaction. Chloromethylation and quaternization reactions of the precursors provided thin and ductile QPAF membranes with ion exchange capacity (IEC) ranging from 0.79 to 1.74 meq g−1. The QPAF membranes exhibited a phase-separated morphology based on the hydrophilic/hydrophobic differences in the main chain structure. The QPAF membrane with an optimized copolymer composition and IEC = 1.26 meq g−1 showed high hydroxide ion conductivity (95.5 mS cm−1 in water at 80 °C), excellent mechanical properties (large elongation at break (218%)), and reasonable alkaline stability at 80 °C. An alkaline fuel cell using the QPAF as the membrane and electrode binder achieved the maximum power density of 139 mW cm−2 at a current density of 420 mA cm−2.

Sulfonated poly(arylene ether phosphine oxide ketone) block copolymers as oxidatively stable proton conductive membranes.

The introduction of triphenylphosphine oxide moiety into the hydrophilic segments of aromatic multiblock copolymers provided outstanding oxidative stability and high proton conductivity. Our designed multiblock copolymers are composed of highly sulfonated phenylene ether phosphine oxide ketone units as hydrophilic blocks and phenylene ether biphenylene sulfone units as hydrophobic blocks. High molecular weight block copolymers (Mw = 204-309 kDa and Mn = 72-94 kDa) with different copolymer compositions (number of repeat unit in the hydrophobic blocks, X = 30, and that of hydrophilic blocks, Y = 4, 6, or 8) were synthesized, resulting in self-standing, transparent, and bendable membranes by solution-casting. The block copolymer membranes exhibited well-developed hydrophilic/hydrophobic phase separation, high proton conductivity, and excellent oxidative stability due to the highly sulfonated hydrophilic blocks, which contained phenylene rings with sulfonic acid groups and electron-withdrawing phosphine oxide or ketone groups.

Synthesis and Properties of Oligophenylene-Layered Polymers

We report syntheses of phenylene-, biphenylene-, and terphenylene-layered polymers with a xanthene scaffold by the modified Suzuki-Miyaura coupling reaction. Their optical properties were studied in detail. The polymer end-capped by nitrobenzene units, which act as fluorescence quenchers, exhibited the photo-excited energy transfer from the layered oligophenylenes to the terminal units.

Proton conductive aromatic block copolymers from a new bistriazole monomer

We have designed and synthesized a new bistriazole compound, 3,3′-(1,3-phenylene)bis[4-phenyl-5-(4-fluorophenyl)-4H-1,2,4-triazole], as a comonomer for a series of sulfonated block poly(arylene ether) copolymers. The bistriazole was successfully synthesized from isophthalic dihydrazide and 4-fluorobenzoyl chloride via bisoxadiazole. The bistriazole monomer was polymerized with 4,4′-biphenol or 4,4′-dihydroxydiphenyl ether to obtain hydroxyl-terminated hydrophobic oligomers, which were copolymerized with sulfonated oligomers to obtain the title block copolymers. The block copolymers were high-molecular-weight (Mw = 91–500 kDa) and provided tough and bendable membranes by solution casting. Because of the sequenced block copolymer structures, the membranes exhibited hydrophilic/hydrophobic phase-separated morphology as confirmed by scanning transmission electron microscopic (STEM) images. The membranes showed proton conductivity under humidified conditions; the highest proton conductivity was 6 × 10−2 S cm−1 at 95% relative humidity (RH) and 80 °C. The membranes were mechanically stable with high storage moduli (ca. 109 Pa) and loss moduli (ca. 108 Pa). These mechanical properties were independent on the ion exchange capacity (IEC) of the membranes. The triazole groups were effective in improving the mechanical and oxidative stability of the sulfonated poly(arylene ether) block copolymer membranes.

Amphiphilic Hybrid π-Conjugated Polymers Containing Polyhedral Oligomeric Silsesquioxanes

Amphiphilic hybrid π-conjugated polymers that have polyhedral oligomeric silsesquioxanes on their side chains have been successfully synthesized by the Sonogashira-Hagihara polycondensation reaction. The obtained polymers were studied with ultraviolet-visible absorption and photoluminescence spectra. In these polymers, the π-conjugation length was extended along the poly(p-phenylene-ethynylene) backbone. Furthermore, the content of the POSS substituents can influence the aggregation behavior of the polymers and subsequent luminescent properties.

Design of flexible polyphenylene proton-conducting membrane for next-generation fuel cells

A novel design has enabled development of polyphenylene ionomer membranes that address major issues for fuel cell applications. Proton exchange membrane fuel cells (PEMFCs) are promising devices for clean power generation in automotive, stationary, and portable applications. Perfluorosulfonic acid (PFSA) ionomers (for example, Nafion) have been the benchmark PEMs; however, several problems, including high gas permeability, low thermal stability, high production cost, and environmental incompatibility, limit the widespread dissemination of PEMFCs. It is believed that fluorine-free PEMs can potentially address all of these issues; however, none of these membranes have simultaneously met the criteria for both high performance (for example, proton conductivity) and durability (for example, mechanical and chemical stability). We present a polyphenylene-based PEM (SPP-QP) that fulfills the required properties for fuel cell applications. The newly designed PEM exhibits very high proton conductivity, excellent membrane flexibility, low gas permeability, and extremely high stability, with negligible degradation even under accelerated degradation conditions, which has never been achieved with existing fluorine-free PEMs. The polyphenylene PEM also exhibits reasonably high fuel cell performance, with excellent durability under practical conditions. This new PEM extends the limits of existing fluorine-free proton-conductive materials and will help to realize the next generation of PEMFCs via cost reduction as well as the performance improvement compared to the present PFSA-based PEMFC systems.

Intrapolymer Heck reaction for proton conductive ladder-type aromatic block copolymers

A novel polymer synthetic method, the intrapolymer Heck reaction, provided ladder-type ionomer membranes with excellent proton conductivity (221 mS cm−1 at 80 °C and 90% relative humidity) and mechanical strength over a wide range of humidity (ca. 0–90% relative humidity) at 80 °C.

A sulfonated polybenzophenone/polyimide copolymer as a novel proton exchange membrane

A sulfonated polybenzophenone/polyimide block copolymer membrane exhibited high proton conductivity, good dimensional and mechanical stabilities, and low gas permeability, which are attractive for fuel cell applications.