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A04. Theories and Modeling

To understand the hierarchical structures and dynamics of soft matter, it is important to establish a linkage between different models on different length and time scales. The A04 team, in cooperation with the other 3 teams, provides suitable theories and models for the phenomena on the individual scales as well as constructs unified multi-scale models that range from the microscopic to macroscopic scales.

Research Projects

Kawakatsu group
Dynamical Theories on Inhomogeneous Polymer Systems Raging from the Microscopic to Macroscopic Scales
[ Leader ] [ Collaborator ] [ Collaborator ]
Toshihiro Kawakatsu
Tohoku University
Tetsuo Deguchi
Ochanomizu University
Katsuhiko Satoh
Tohoku University
research subject
In dense polymeric systems, the important factors that determine the macroscopic flow properties are not only the microscopic chain dynamics (e.g. the stretching and entanglements of the chains, formation of the networks) but also the inhomogeneity in the mesoscopic scales such as the interfaces in the phase separated systems or the surfaces of dispersed particles. In order to understand these complex multi-scale phenomena in polymeric systems, it is important to combine several models and theories on different length and time scales. In our research group, we will develop the density functional theories (e.g. self-consistent field theory and the Ginzburg-Landau theory) to predict the structure and dynamics of the mesoscopic inhomogeneity of the polymeric system based on the microscopic information on the chain architecture. For this purpose, we will combine these density functional theories with microscopic models of the molecular dynamics of the constituent polymer chains or with the models of liquid-crystalline polymers. As practical applications of these theories, we study viscoelastic properties of dense polymeric systems. We also discuss, in cooperation with the experimental groups, structural phase transitions of mesophases of polymers, dynamics of reactive polymers, gelation of liquid-crystalline polymers and so on.
Doi group
Rheology of Microfluidics in Polymer Solutions
[ Leader ] [ Member ] [ Collaborator ]
Masao Doi
University of Tokyo
Tohru Okuzono
Nagoya City University
Tetsuo Yamaguchi
University of Tokyo
research subject
Flows, adhesion, and drying of polymer solutions on solid substrates are phenomena of great importance in a wide variety of industrial applications, such as coating, printing, manufacturing of electronic devices, etc. However, there is no fundamental research on these interfacial phenomena that involve many physical processes which affect each other, such as solvent evaporation, wetting, network formation (gelation) and deformation, and void formation due to negative pressure. The aim of this research is to construct theoretical models, in various scales, of the governing processes (e.g. motion of contact lines, formation of gel phase, formation of voids, etc) in the flow dynamics of polymer solutions in micro-scale regions. Based on these models, we build a multi-scale simulator which is useful for real applications. Moreover, we carry out experiments with other research group's members to verify our theory and numerical simulations.
Onuki group
Studies on Charge-Polarization-Induced New Phases and Shear-Induced Non-Equilibrium Phenomena in Soft Matter
[ Leader ] [ Member ] [ Member ] [ Member ]
Akira Onuki
Kyoto University
Makoto Yao
Kyoto University
Hideki Seto
Institute of Materials Structure Science, High Energy Accelerator Research Organization
Ryoichi Yamamoto
Kyoto University
[ Member ] [ Collaborator ]
Toshiji Kanaya
Kyoto University
Takeaki Araki
Kyoto University
Takimoto group
Dynamics and Rheology of Chain-Like Structures and Network Structures in Soft Matter
[ Leader ] [ Member ] [ Member ]
Jun-ichi Takimoto
Yamagata University
Tomonori Koda
Yamagata University
Takashi Taniguchi
Kyoto University
research subject
In many soft matters of interests, it is common that various kinds of string or network like structures exist and their deformation and dynamics govern the rheology of the matter. The string-like structure may be either permanent (such as polymer chains) or temporary (various string-like aggregates). The network structure may also permanent (chemical gels) or temporary (entanglements among polymer chains, physical gels, etc.). Our aim is to understand, by theory and simulations in meso-scale level, the deformation, breakage and re-formation of these structures under strain and flow, and predict the rheology of the soft matters. We are currently focusing mainly on entangled polymers, disk-like liquid crystals and associating liquid crystals.
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Public Participation Research (2009-2010)

Miyazaki group
Glass Transition and the Nonlinear Rheology of Colloidal Systems
[ Leader ]
Kunimasa Miyazaki
University of Tsukuba
research subject
Our project aims at unveiling mysteries of the glass transition through the studies on various soft condensed matters. Especially we focus on suspensions of spherical colloids and investigate their slow dynamics and anomalous nonlinear rheology that are the hallmarks of the glassy systems. Specific topics are (1) understand the microscopic origin of the fragility, or the non-Arrhenius relaxation near the glass transition point and (2) to unravel the mechanical/dynamical properties of the jamming transition (a glass transition at zero-temperature) and its relation to the transition at finite temperatures.
Sumi group
Development of a Liquid State Approach for Multiscale Analysis of Soft Matter and its Applications
[ Leader ]
Tomonari Sumi
Toyohashi University of Technology
research subject
In this study, we develop a liquid state approach for soft matters and apply it to both the soft matters and biological systems. For the purpose, we solve theoretical and technical problems in the liquid state approach for both concentrated polymer solutions and block copolymer solutions, and aim to construct a multiscale method for analyzing the relation between the mesoscopic structures and the intra- and inter-molecular structures in the soft matters.
Koga group
Theory of First-order and Continuous Wetting Transitions at Soft Interfaces
[ Leader ]
Kenichiro Koga
Okayama University
research subject
In a system of three fluid phases in equilibrium, one phase may intrudes at ("wet") the interface of the other two or the three phases meet at a line of common contact. With varying thermodynamic state there may be a transition between these two modes of three-phase equilibrium, which is a wetting transition. The wetting transition may be first-order or continuous, depending on the chemical compositions and the thermodynamic states. A goal of this research project is to understand what makes the wetting transition discontinuous or continuous. We examine mean-field density functional models of first-order and continuous wetting transitions and then study a hybrid model that may exhibit the two kinds of transitions.
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