Hot Topics

Vol. 61, No. 5, May (2012)

Polymer Electrolyte Membranes and their Ion Conduction Mechanisms for Improving the PEFC Performances
Takeo YAMAGUCHI
Chemical Resources Laboratory, Tokyo Institute of Technology

We developed a novel proton conducting membrane with heterophase interface proton channels. The membrane shows high proton conductivity at broad RH range with high hydrothermal and mechanical stability. The membrane is fabricated by a combination of a capping and a pore-filling technology. The capping phenomenon is multipoint inter-adsorption of the electrolyte polymer to a nano-sized inorganic particle, results in nano-channels of heterophase interfaces between inorganic particles and polymers at which rapid proton conduction can occur. The nano-sized structure can be kept in micro-pores of a porous membrane that connect to each other. The protons rapidly conduct through the membrane.
Polymer Preprints, Japan 2011, 60, 49.

Molecular Design for Repairing Polymer by Using Dynamic Bonds
Naoko YOSHIE
Institure of Industrial Science, The University of Tokyo
The repairing property of polymers offers extension of working life and enhancement of safety performance of polymer materials. In this paper, repairing behavior of network polymers with reversible reactivity is described. A network polymer with low crystallization rate was shown to be a thermo-responsive repairing polymer in which crack healing is induced by a prompt thermal stimulus. The molecular mobility in the supercooled state promotes the reformation of dynamic bonds bridging the cut surfaces, resulting in the repairing. Thermally stable repairing polymer was also developed by using the Diels-Alder reaction between anthracene and maleimide.
Polymer Preprints, Japan 2011, 60, 4.

Molecular Pictures of Tacticity Effects on the Solubility of Acrylamide Polymers
Yukiteru KATSUMOTO
Graduate School of Science, Hiroshima University
The tacticity of acrylamide polymers drastically affects their water solubility. To reveal the physical background of this phenomenon, we consider a balance between the intra- and intermolecular interactions. The dimer and trimer molecular compounds are very useful to investigate this balance. For poly(N-isopropylacrylamide) (PNiPAm) and poly(N-ethylacrylamide), the solubility of the dimer model compounds to water shows a clear stereoregularity dependence; the meso type dimer is more hydrophobic than that the raceme one. This result is in good harmony with the experimental result that the meso-rich polymers are more hydrophobic than the racemo-rich ones. The molecular mechanics calculations reveal that the racemo configuration is advantageous in the hydration, while the meso configuration is favorable for the intramolecular interaction.
Polymer Preprints, Japan 2010, 59, 3186.
Polymer Preprints, Japan 2011, 60, 3526.

Color-Tunable Ge Nanoparticles with Organic Probe
Naoto SHIRAHATA1-3, Daigo HIRAKAWA1,4, and Yoshio SAKKA1,4
1National Institute for Materials Science (NIMS), 2WPI-MANA, 3JST-PRESTO, 4University of Tsukuba
A color-tunable light emission in the UV-Visible range was achieved by structural control of Ge nanoparticles (NPs). The Ge NPs were prepared through a novel process with "laser chemical synthesis", which allows the simultaneous achievement of NP formation and subsequent attachment of an alkyl ligand in a single step by performing laser ablation of a Ge target in unsaturated hydrocarbon chains. As shown in the Figure, the NP samples showed the structural dependent light emission properties when excited with a handheld UV lamp, respectively. The PL quantum yields of these samples were estimated to be more than 4%, which is high enough to be used as fluorescent labels. The appearance of structural dependent color-tunable photoluminescence at single light excitation allows the parallel detection and monitoring of different molecular recognition events under microscopic observation.
Polymer Preprints, Japan 2011, 60, 1093.

Heterogeneity in Soft Materials Detected by Optical Tweezers
Atsuomi SHUNDO and Keiji TANAKA
Department of Applied Chemistry, Kyushu University
Optical tweezers enable us to gain direct access to viscoelastic properties of soft materials at the micrometer scale. In this method, a probe particle, which is dispersed in a medium to be measured, is trapped by a laser beam and sinusoidally oscillated. The response movement of the particle reflects viscoelastic properties of the surrounding medium. By using this technique, we succeeded in detecting dynamic heterogeneity in supramolecular hydrogel, which was based on a micelle-like self-assembly of peptide amphiphiles to produce a fibrous network. Interestingly, the network, and therefore the heterogeneity, can be easily regulated by varying the temperature used to dissolve the gelator in water. Also, optical tweezers could be applied to examine heterogeneity of an aqueous solution in which radical polymerization of an ionic monomer proceeded.
Polymer Preprints, Japan 2011, 60, 136.
Chem. Commun., 2011, 47, 8844.