Drying dissipative structures of lightly cross-linked poly(2-vinyl pyridine) cationic gel spheres stabilized with poly(e
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ORIGINAL CONTRIBUTION
Drying dissipative structures of lightly cross-linked poly (2-vinyl pyridine) cationic gel spheres stabilized with poly (ethylene glycol) in the deionized aqueous suspension Tsuneo Okubo & Syuji Fujii & Kodai Aono & Yoshinobu Nakamura
Received: 9 September 2012 / Accepted: 27 September 2012 / Published online: 13 October 2012 # Springer-Verlag Berlin Heidelberg 2012
Abstract Drying dissipative patterns of deionized and colloidal crystal-state suspensions of the cationic gel spheres of lightly cross-linked poly(2-vinyl pyridine) stabilized with poly(ethylene glycol) were observed on a cover glass, a watch glass, and a Petri glass dish. Convectional patterns were recognized with the naked eyes. The broad rings were observed in the drying pattern and their size and width decreased as gel concentration decreased. Formation of the monodispersed agglomerated particles and their ordered arrays were observed. This work clarified the formation of the drying microscopic structures of (a) ordered rings, (b) flickering ordered spoke-lines, (c) net structure, and (d) lattice-like ordered structures of the agglomerated particles. The ordering of the agglomerated particles of the cationic gel spheres is similar to that of the anionic thermo-sensitive gel spheres of poly(N-isopropyl acrylamide). The role of the electrical double layers around the agglomerated particles and the interaction of the particles with the substrates during dryness are important for the ordering. The microscopic drying patterns of gel spheres were different from those of linear-type polymers and also from typical colloidal hard spheres, though the macroscopic patterns such as broad ring formation at the edges were similar to each other. The Electronic supplementary material The online version of this article (doi:10.1007/s00396-012-2825-5) contains supplementary material, which is available to authorized users. T. Okubo (*) Institute for Colloidal Organization, Hatoyama 3-1-112, Uji, Kyoto 611-0012, Japan e-mail: [email protected] S. Fujii : K. Aono : Y. Nakamura Department of Applied Chemistry, Faculty of Engineering, Osaka Institute of Technology, 5-16-1, Ohmiya, Asahi-ku, Osaka 535-8585, Japan
addition of sodium chloride shifted the microscopic patterns from lattice to net structures. Keywords Cationic gel spheres . Poly(2-vinyl pyridine) . Drying pattern . Dissipative structure . Ordered array . Agglomeration . Convectional pattern
Introduction Most structural patterns in nature form via self-organization accompanied with the dissipation of free energy and in the nonequilibrium state. In order to understand the mechanisms of the dissipative self-organization of the simple model systems, instead of the much complex nature itself, the authors have been studying the convectional, sedimentary, and drying dissipative patterns during dryness of solutions and suspensions as systematically as possible, though these three kinds of structures are correlated strongly and overlapped to each other [1–3]. It should be mentioned here that th
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