[Seminar] Synchrotron X-ray Scattering and Spectroscopy Applied to Soft Matter/ Design and Characterization of Hybrids/ Surface and Interface Structure of Polyelectrolyte Brushes by Prof. Atsushi Takahara, Kyushu University

Speaker: Prof. Atsushi Takahara 高原 淳　　

Synchrotron radiation (SR) produces light that is highly brilliant than conventional X-ray sources.  Photon energy covers from soft X-ray, tender X-ray to hard X-ray. By utilizing wide energy range and high quality of light, various scattering and spectroscopic methods can be applied to various soft materials. In this presentation, our recent researches on appliation of synchrotron X-ray scattering and spectroscopy to soft matter are summarized.

Abstract of 'Design and Characterization of (Polymer/Natural Inorganic Nanotube) Hybrids

Surface functionalization of tubular nano-clays of imogolite and halloysite using the selective binding of organophosphonic acids and organosilane compounds, and the use of the surface modified nanotubes in polymer hybrids were studied. Surface modification of imogolite with alkyl phosphonic acid salt through the specific interaction of phosphonic acid and the exterior alumina sites of imogolite was presented. SI-ATRP was performed with the selectively adsorbed phosphonic acid functionalized ATRP-initiator to prepare polymer brushes on the imogolite surface. Selective modification of halloysite nanotube exterior and inner surfaces was demonstrated. Aqueous phosphonic acid binds to alumina sites at the tube lumen to make the lumen hydrophobic. Subsequent modification with organosilane affords bifunctionalized halloysites with both the lumen and exterior surface modified. Loading of hydrophobic organic compound to the modified lumen was confirmed. SI-ATRP was performed through the selectively adsorbed DOPA-functionalized ATRP-initiator to prepare polymer brushes on the nanotube lumen. Also, surface modified halloysite was applied for preparation of novel intelligent polyurethane nanocomposites with improved thermal stability and mechanical properties.

Abstract of 'Surface and Interface Structure of Polyelectrolyte Brushes'

Soft interfaces offer fascinating opportunities for addressing numerous problems of both academic and industrial interests: high-quality functional or protective coatings, composite materials, surface engineered particles, metal-organic interfaces, biological applications, micro-patterning, etc. Polymers chemically grafted to the surface of substrates are typical soft interfaces known as polymer brushes. Surfaces covered with polyelectrolyte brushes are particularly attractive because of their potential applications including adhesion, antifouling, biocompatibility and water lubrication systems. In this presentation, our recent researches on control of wettability and adhesion through precise design of soft interfaces such as a polyelectrolyte brush surface are presented. We started from fundamental science including precise polyelectrolyte synthesis and solution characterization of polyelectrolytes, characterization of polymer brush at water interfaces, and water structure in polymer brushes. On the basis of these fundamental studies, we have successfully achieved 1) superhydrophilicity, 2) antifouling properties, 3) super-lubricant behavior, and 4) cell-surface interaction control.