Hot Topics

Vol. 61, No. 2, February (2012)

Morphology Control of Aromatic Polymers Using Phase Separation during Polycondensation
Kunio KIMURA
Graduate School of Environmental Science, Okayama University

Wholly aromatic polymers are well known as a substantial class of high-performance materials because of their excellent properties. However, their high melting temperature and poor solubility usually make them inaccessible for processing by conventional techniques. Precise morphology control of intractable polymers has been studied to overcome the antagonistic problem between intractability and properties by using reaction-induced phase separation during isothermal polymerizations. This paper presented the preparation of various morphologies of aromatic polymers such as needles, fibers, ribbons, spheres and so on. The polymer molecules orientation was simultaneously controlled with morphology, and they aligned along the long axis of the needles, fibers and ribbons. This morphology control method cannot be limited by the intractability of the polymers, and therefore it is very desirable to create novel materials possessing their essential properties.
Polymer Preprints, Japan 2011, 60, 58.

Dismantlable Adhesion Using Acrylic Block Copolymers for On-Demand Debonding
Akikazu MATSUMOTO
Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University
Dismantlable adhesion as on-demand debonding technology has recently attracted great attention because it is useful for materials recycling and saving energy. We reported a new dual-locked dismantlable system for pressure-sensitive adhesion using block copolymers containing poly(tert-butyl acrylate) and poly(2-ethylhexyl acrylate) segments in the presence of a photochemical acid generator. This new adhesion system can easily be debonded due to a change in the properties of the adhesives by acid-catalyzed deprotection uniquely occurring during photoirradiation followed by postbaking. During the evaluation of the adhesive properties using a 180° peel test, a drastic change in the adhesive strength of the block copolymers was observed in response to the dual external stimuli consisting of UV irradiation and the subsequent heating.
Polymer Preprints, Japan 2011, 60, 61.

Stable Nitrile N-Oxide Chemistry: A New Chemical Ligation Tool to Common Polymers
Yasuhito KOYAMA*, Morio YONEKAWA, Kaori MIURA, Tohru MATSUMURA, and Toshikazu TAKATA
Department of Organic and Polymeric Materials, Tokyo Institute of Technology
Several techniques of chemical ligation have been reported for the purpose of selectively combining large molecules to afford highly sophisticated macromolecular architectures. One of the best solutions is click chemistry based on Huisgen dipolar cycloaddition of azides and alkynes that has recently generated particular interest as a powerful synthetic tool for molecular integration. However, the explosiveness of the multitopic azides in addition to the requirement of Cu(I) catalyst leads to some limitations in their use. Recognizing these issues, we noted the potential usefulness of nitrile N-oxide as the substitute for azide, which undergoes the efficient [2+3] cycloaddition with not only alkynes but also alkenes and nitriles to selectively give the corresponding heterocycles. Herein, we describe the utility and productivity of new chemical ligation tools exploiting kinetically stabilized nitrile N-oxides.
Polymer Preprints, Japan 2011, 60, 93.
Kobunshi Ronbunshu 2011, 68, 147.

Shish-Kebab Formation Process of Polyethylene During Uni-Axial Draw with Small-Angle X-Ray and Neutron Scattering Measurements
Go MATSUBA
Department of Polymer Science and Engineering, Graduate School of Science and Engineering, Yamagata University
We have studied structure development during drawing process of blends of low molecular weight deuterated polyethylene and high molecular weight hydrogenated polyethylene at 125℃ just below the nominal melting temperature by means of in-situ small-angle x-ray scattering (SAXS) and small-angle neuron scattering (SANS) techniques in order to clarify the structure formation mechanism. In the early stage, it was found in the SAXS pattern that isotropic lamella crystals were oriented and then we observed the oriented stacked lamella (kebab). The steak scattering appeared in the normal direction in the SANS but not in the SAXS, suggesting that the high molecular weight polyethylene aligned along the draw direction to form the shish. On further draw, the kebabs disappeared because polymer chains are pulled out from the lamella crystals and disentangled, and finally merged into the shish structure.
Polymer Preprints, Japan 2011, 60, 96.

Room-Temperature Ionic Liquids Based on POSS
Kazuo TANAKA* and Yoshiki CHUJO
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University
Nanostructured polymeric materials have attracted attention as the platforms for developing new series of ionic liquids (IL) because there is much potential to detect advanced functions originating from structural features. Polyhedral oligomeric silsesquioxanes (POSS) are used as nano building blocks for constructing functional materials. The rigid silica cube shows high thermal stability. Moreover, POSS can form star-shaped structures and isolate each substitution group on the vertices. Herein, we report the synthesis of POSS-based room temperature-ILs, which have melting temperatures below 25℃. By connecting ion pairs to POSS, a lowering of the melting temperature and enhancement of the thermal stability were simultaneously accomplished. The rigidity and the cubic structure of POSS can contribute to POSS-enhanced thermal properties.
J. Am. Chem. Soc. 2010, 132, 17649.
Polym. J. 2011, 43, 708.

Temperature-induced Hydrogel Based on Collagen-mimic Dendrimers
Chie KOJIMA
Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University
Collagen is classically used as a biomaterial, which forms hydrogel under physiological conditions. Dendrimers are a potential functional polymer. We previously synthesized polyamidoamine (PAMAM) dendrimers modified with collagen model peptides such as proline-(hydroxy)proline-glycine (Pro-Pro-Gly or Pro-Hyp-Gly) repeats, named collagen-mimic dendrimers. In this study, we focused on the (Pro-Hyp-Gly)10-modified dendrimer. Fully peptide-modified dendrimer was synthesized. The dendrimer efficiently formed the triple helical structure with thermal stability. Interestingly, this dendrimer formed the heat-induced self-assembly and hydrogel. The assembly may be induced by the rearrangement of bound water molecules to the triple helix. The dynamic viscoelastic analysis indicated that the hydrogel (15 wt%) was stiff and thermally stable. This kind of heat-induced collagen-mimic hydrogel is novel.
Polymer Preprints Japan 2011, 60, 1288. Soft Matter 2011, 7, 8991.