Polymers - Vol. 58, No. 8 (August, 2009)

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Vol. 58, No. 8 August,( 2009)

Developments of Novel Functional Materials for Carbon Nanotube/Polymer Hybrid
Tsuyohiko FUJIGAYA
Department of Applied Chemistry, Faculty of Engineering, Kyushu University

We have been developing a wide range of polymer/carbon nanotube (CNT) composites aiming at the creation of new functional materials. One of our resent results is a polybenzimidazole (PBI)/CNT composite. The thin wrapping of the PBI around CNT enables efficient and homogeneous Pt loading on the CNT via a coordinative mechanism. The transmission electron microscope measurements revealed the new composite showing ideal triple phase boundary structure and possessing a large electrochemically active area. Membrane-electrode assembly composed of PBI film and CNT/PBI/Pt composite layers was successfully operated as a fuel cell under 100Ž in dry condition. Polymer Preprints, Japan 2008, 57, 1439.

AMajor Breakthrough in Living Cationic Polymerization
Sadahito AOSHIMA* and Shokyoku KANAOKA
Department of Macromolecular Science, Graduate School of Science, Osaka University
We have developed new methods that allow precise control of the structure and molecular weight of polymers. Our recent systematic investigation of Lewis acids for cationic polymerization has revealed that a variety of metal halides can induce the living polymerization of vinyl ethers and styrenes. The addition of a suitable base and appropriate selection of an acid catalyst were found to be crucial to the success of the following new types of living polymerization: (1) ultra-fast living polymerization in seconds and SnCl4-induced living polymerization of various monomers, (2) heterogeneously-catalyzed living polymerization with iron oxides or heteropoly acids, and (3) selective synthesis of star-shaped polymers with a narrow MWD and reusable gold nanocluster catalysts stabilized by the star-shaped polymers. Polymer Preprints, Japan 2009, 58, 46. Kobunshi 2008, 57, 633.

Design of New Hydrogel Biomaterials by Nanogel Engineering
Kazunari AKIYOSHI
Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University
Functional nanogels have been designed by the self-assembly of various associating polymers. In particular, cholesterol-bearing polysaccharides(CHP) formed physically cross-linked nanogels by the self-assembly in water. The nanogels trap proteins by mainly hydrophobic interaction and show chaperon-like activity. They are useful for polymeric nanocarriers especially in protein delivery. Macrogels with well-defined nanostructures were obtained by self-assembly and chemically cross-linking of the nanogels as building blocks. Acryloyl or methacryloyl group-modified CHP was synthesized as reactive nanogels. By using the nanogels, nanogel cross-linking nanoparticles, hydrogels, sheet film and nanogel-coating materials were developed. Nanogel engineering is an efficient and versatile technique for preparing functional hydrogels in drug delivery and regenerative medicine. Polymer Preprint, Japan 2009, 58, 41.

Highly Sensitive Photopolymers Enhanced by Phototriggered Base Proliferation Reactions
Koji ARIMITSU
Department of Pure and Applied Chemistry, Tokyo University of Science
Novel photo reactive base amplifiers for highly sensitive photopolymers utilizing base-catalyzed reactions have been developed. The base amplifiers photochemically generate a catalytic amount of base molecules, which trigger base-catalyzed decomposition of the base amplifiers to liberate newborn bases, thus leading to autocatalytic decomposition. This process is referred to as base proliferation. Boosting the concentration of photo generated catalysts, in this case amines, should improve photosensitivity markedly. The combination of the photo reactive base amplifiers with a base-sensitive polymer showed much higher photosensitivity when compared to conventional photopolymers relying on base-catalyzed transformations. Polymer Preprints, Japan 2009, 58, 1.

Fiber Structure and Deformation Process of PBO Fiber
Tooru KITAGAWA
Toyobo Co., Ltd. Research Center
The history of super fibers, mainly concerned with high-modulus high-strength fibers, has dated back to 1960s when the p-aramid fiber was developed. Commercialization of co-aramid fiber and polyarylate fiber was followed. The development of PBO fiber was also stimulated with that success and bore fruit. It was commercialized in the name of Zylon(R) in 1998. Design and alignment of molecules and crystallites in the fiber is important. The relationship between fiber structure and properties has been well studied with X-ray diffraction, small-angle X-ray scattering, microscopy and molecular-vibrational methods, which gave a fiber structural model in summary. A new coagulation method was proposed to improve fiber modulus. Mechanical deformation process of the fiber under stress was analyzed and discussed.
Polymer Preprints, Japan 2009, 58, 10.

pH-Responsive Fusogenic Liposomes for Intracellular Delivery
Kenji KONO
Dept. of Applied Chemistry, Osaka Prefecture University
We developed pH-responsive liposomes, which generate fusogenic activity under mildly acidic conditions, by surface modification of stable liposomes with poly(glycidol) derivatives having carboxyl groups, such as SucPG and MGluPG. We found that MGluPG provided stronger fusion ability to egg yolk phosphatidylcholine liposomes than SucPG, because of the higher hydrophobicity of MGluPG side groups. When taken up by cells, MGluPG-modified liposomes achieved delivery of contents into cytosol of target cells more quickly and more efficiently than SucPG-modified liposomes. We observed that antigen-loaded MGluPG-modified liposome induced activation of cellular immunity in mice after nasal administration. Also, MGluPG-modified liposomes strongly enhanced gene transfection into cells. Thus, these pH-sensitive fusogenic liposomes were promising as carriers that deliver bioactive molecules into cytosol of the target cells.
Polymer Preprints, Japan 2009, 58, 43.

Reworkable UV Resins for Mold Replication in Imprint Lithography
Masamitsu SHIRAI
Department of Applied Chemistry, Osaka Prefecture University
Most studies on UV resins have been focusing on the enhancement of curing rate and the improvements of physical, thermal, and mechanical properties of cured resins. However, UV curable resins with degradable characteristics, which is named reworkable UV resin, could be used as environmentally friendly materials and novel functional materials. Multi- functional (meth)acrylates having a hemiacetal ester linkage in a molecule were prepared as a reworkable UV resin. These monomers containing a photo-radical initiator and a photo-acid generator were curable upon irradiation at 365 nm and the cured resins were degraded on irradiation at 254 nm. These UV resins were applied to make a plastic replica of mold for imprint lithography. First, primary patterns of the reworkable UV resin were obtained by UV imprint process using 365 nm light. Then, using the primary patterns as a mold, secondary patterns (plastic replica of a mold) of conventional UV curable resin were obtained by removing the primary patters of rewokable UV cured resins on irradiation at 254 nm. Polymer Preprints, Japan 2009, 58, 7.

Multifunctional Designer Catalysts and Polymers via Living Radical Polymerization
Takaya TERASHIMA* and Mitsuo SAWAMOTO
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University
Multifunctional designer catalysts and polymers were developed via ruthenium-catalyzed living radical polymerization, especially focused on 1) sequential or concurrent tandem catalysis and 2) core-functionalized star polymers. The key is to utilize (co)catalysts with high controllability and tolerance to polar functional groups, and catalytic versatility. Typically, a ruthenium catalyst efficiently induced sequential hydrogenation of the terminal halogen in living polymers via in-situ catalyst transformation, and the catalyst with a lewis acid cocatalyst and an alcohol solvent directly led to gradient copolymers via concurrent transesterification of ester-based monomers. Core-functionalized designer star polymers carrying metals, PEG, and imprint core, directly prepared with ruthenium catalysts, efficiently perform unique catalysis and selective molecular recognition. Polymer Preprints, Japan 2009, 58, 108.

Coordination Polymerization of Polar Vinyl Monomers Catalyzed by Palladium Catalyst
Kyoko NOZAKI
Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo
Unlike the conventional post-polymerization functionalization of linear polyethylene (HDPE), direct copolymerization of ethylene with a polar vinyl monomer to provide a linear copolymer has been achieved by using palladium/ phosphine-sulfonate complexes. Isolation of an alkylpalladium complex with well-defined structure enabled us to develop ethylene/acrylonitrile and ethylene/ vinyl acetate copolymerizations. The unique role of the unsymmetrical bidentate ligand was elucidated by theoretical calculations as follows. The stronger trans effect of phosphine compared to sulfonate lowered the TS for the ethylene insertion which took place immediately after polar monomer insertion (TS 1) and elevated the TS for ƒÀ-hydride elimination from an alkylpalladium species (TS 2). Although an alternative TS for b-hydride elimination (TS 3) is located at much lower level than TS 2, TS 3 was suggested to be hardly accessible under the polymerization conditions. Polymer Preprints, Japan 2009, 58, 49.

Polymer Electrolyte Membranes and their Ion Conduction Mechanisms for Improving the PEFC Performances
Takeo YAMAGUCHI
Tokyo Institute of Technology Chemical Resources Laboratory
We found that protons rapidly conduct through unfreezable and bound water in a pore-filling electrolyte membrane (PF-membrane), although many ions usually conduct through free water contained in polymer electrolytes. PF-membrane is a unique membrane that can suppress the swelling of filled sulfonated poly(arylene ether sulfone) (SPES) because of its rigid polyimide substrate. Without being constrained by the PF-membrane, this unique proton conduction through the structured water and highly concentrated sulfonic acid groups will help to develop future polymer electrolytes, particularly in the fuel cell field. Also, we found that utilization of an interface between nano- particle and polymer electrolyte polymer facilitates the proton conduction. Polymer Preprints, Japan 2009, 58, 4.

Does Phase Separation Really Occur in Dilute Aqueous PNIPA Solutions?
Takenao YOSHIZAKI
Department of Polymer Chemistry, Kyoto University
Phase behavior of dilute aqueous solutions of poly(N- isopropylacrylamide) (PNIPA) was found not to be as simple as usually considered. As shown in the figure, the transmittance of light passing through a solution approaches a constant value between 0 and 100% even at a temperature slightly higher than its cloud point, indicating that macroscopic phase separation does not occur spontaneously at the cloud point and therefore the cloud-point curve dose not correspond to the binodal. Further, the cloud point in aqueous PNIPA solutions is shown to be governed not only by the hydrogen bonds between PNIPA and surrounding water molecules but also by the end group and primary structure of PNIPA chains. Polymer Preprints, Japan 2009, 58, 52.

Investigation for Controlled Condensation Polymerization of Amino Acids
Tsuyoshi ANDO
Graduate School of Materials Science, Nara Institute of Science and Technology
In general, controlled/living polymerization of condensation polymerization is not applicable and only limited to certain monomers because the reactivity of the condensing groups in the polymer termini is almost same as that in the monomer to induce random condensation. To overcome the problem, we investigated the molecular weight control of the condensation polymerization of amino acids in the presence of carboxylic acid, condensation reagent and additive by continuous addition of monomer. Nipecotic acid (NA; monomer) was polymerized by continuous addition to a solution containing acetic acid (AcOH; initiator), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDCEHCl; condensation agent), and 1-hydroxybenzotriazole (HOBt) in H2O at 0Ž. The SEC curves of the obtained polymers shifted to higher molecular weight according to the amount of the added monomer (Fig. 1). Polymer Preprints, Japan 2009, 58, 449.