A01. Molecular Dynamics in Structure-Forming Dense Polymer Systems

Dense polymer systems have a huge internal freedom and a high susceptibility thereby forming characteristic structures and exhibiting unique properties under external fields/molecular constraints. The polymer dynamics responsible for this structure formation (e.g., gel formation) is strongly coupled with the structure itself. The A01 team elucidates the basic features of this coupling in various time and length scales.

Research Projects

Watanabe group

Coupling of Phase Separation Dynamics and Chain Motion in Entangled Polymer Systems

 

[ Leader ]	[ Member ]	[ Member ]	[ Collaborator ]
Hiroshi Watanabe Kyoto University	Tadashi Inoue Osaka University	Koji Nishida Kyoto University	Shinichi Sakurai Kyoto Institute of Technology

research subject

The slow dynamics of polymer chains in dense systems is governed by the entanglement. The molecular picture of entanglement has not been well established in heterogeneous systems such as polymer blends, because of a lack of an accurate treatment for the spatial distribution of the entanglement molecular weight and local friction (due to the heterogeneity of the component composition) and the exclusion of chains from unlike phases. In particular, during the phase separation process, the evolution rate of the phase is governed by the chain dynamics, while the phase structure determines the distribution of the entanglement molecular weight and local friction thereby affecting the chain dynamics. Thus, the dynamics of the phase evolution is strongly coupled with the chain dynamics. Nevertheless, no clear molecular picture has been established for this coupling of two classes of dynamics occurring in quite different time/length scales. The aim of this research is to establish this molecular picture on the basis of experimental data accumulated for a variety of dense polymeric systems such as block copolymers, polymer blends, and crystalline polymers.

Matsushita group

Hierarchically Ordered Structures of Supramolecular Complex Polymers and Their Macro-Phase Separation Dynamics

 

[ Leader ]	[ Member ]	[ Member ]	[ Member ]
Yushu Matsushita Nagoya University	Atsushi Takano Nagoya University	Daisuke Kawaguchi Nagoya University	Atsushi Noro Nagoya University

research subject

Self-assembled structures of block- and graft polymers with mesoscopic length scale in condensed systems have been extensively studied both experimentally and theoretically and a variety of achievements have been attained at the molecular level. However, phase transition between nanoscopically-ordered structures and macroscopically phase-separated structures and their dynamics have not been fully investigated yet. Dissociation-association behavior of complex supramacromolecules connected with non-covalent bonds have been focused in this study, and decomposition of chemical bonds and resulting phase separation and its dynamics due to exposition to external fields such as shear flow and temperature will be experimentally observed.

Tanaka group

Molecular Mechanisms of the Sol-Gel Transition

 

[ Leader ]	[ Member ]	[ Member ]
Fumihiko Tanaka Kyoto University	Tsuyoshi Koga Kyoto University	Isamu Kaneda Rakuno Gakuen University

research subject

The ultimate objective of our study is to control the nature of the sol-gel transition in polymer solutions (and melts) on the basis of theoretical and computational analysis on the molecular interactions. The gelling systems we study are roughly classified into three types: partially hydrophobized water-soluble polymers, hydrogen-bonding polymers, and reversibly reacting polymers. (1) Controlling the gel point (in particular, the transition temperature): We attempt to find the sol-gel transition temperature Tg and concentration cg, on the basis of statistical thermodynamics, as functions of the number of functional groups each polymer carries, their position along the chain, and strength of the bond. Results are applied to identify the gel point in the above systems. (2) Controlling the sharpness of the transition: We propose theoretical models of transient networks to study rheological properties of the gels, in particular, to calculate the complex moduli, the number of elastically-effective chains, nonlinear viscosity, etc. near the gel point, and attempt to find new properties of thermoreversible gels. (3) Controlling the gel time: We propose new methods of time-dependent phase diagrams which indicate reaction paths together with phase separation. We calculate the gel time (the time required to reach the gel point), the time required for the gel to melt, transient flow properties (stress overshoot, stress relaxation), etc. under the control of the temperature and pressure.

Shibayama group

Soft Matter Dynamics Analyzed with Photon Correlation Spectroscopy

 

[ Leader ]	[ Member ]	[ Member ]
Mitsuhiro Shibayama University of Tokyo	Kohzo Ito University of Tokyo	Hitoshi Endo University of Tokyo

research subject

Polymer gels belong to polymer condensed matter systems in which polymer chains are bonded via chemically or physically. Polymer gels provide a variety of interesting phenomena, such as volume transition, phase transitions, sol-gel transition, and critical phenomena. Because of cross-linking, polymer gels have dynamic concentration fluctuations and frozen inhomogeneities. Recently, novel cross-linking methods are developed in addition to conventional chemical cross-linking with multifunctional cross-linker, such as plane-cross-linking with disc-like clay platelets, and movable cross-linking with cyclodexitrin dimers. These gels have specific dynamics related to these novel cross-links in addition to the collective diffusion of networks and the translational diffusion of the whole polymer chains. Because of the presence of a variety of dynamics ranging from nanoseconds to seconds, polymer gels can be called "multi-dynamical materials". However, because of their complexity in structure, understanding of polymer gels has not been quite limited. We are exploring the soft matter dynamics of polymer gels in terms of photon-correlation spectroscopy.

Public Participation Research (2009-2010)

Maki group

Chain Aggregation Process in the Phase Separation of Polymer Solutions

 

[ Leader ]
Yasuyuki Maki Gunma University

research subject

Phase separation process of dilute polymer solutions, from aggregation of a few chains to formation of macroscopic droplets of concentrated polymer solution, is studied. The effects of dynamics of polymer chains (chain collapse from coil state to globule state, interpenetration between chains) on the phase separation process are investigated.

Okamoto group

Dynamics of Microphase-Separated Structures Induced by Selective Solvent in Semi-Dilute Solutions of Block Copolymers

 

[ Leader ]	[ Collaborator ]
Shigeru Okamoto Nagoya Institute of Technology	Tadashi Inoue Osaka University

Urayama group

Dynamics of Polymer Network Systems under Various Deformation Modes

 

[ Leader ]
Kenji Urayama Kyoto University

research subject

We investigate the dynamics of polymer network based soft materials such as gels and elastomers under various types of deformation. We examine the dynamics of the nano-carbon dispersed polymer networks and swollen gels in solvent both which exhibit a marked time dependence of mechanical properties. On the basis of the experimental results, we elucidate the physical picture of the dynamics of these systems, and also propose the constitutive equations which describes the dependence of stress on time and strain.

Aoki group

Polymer Dynamics Studied by Direct Imaging of Single Macromolecule

 

[ Leader ]
Hiroyuki Aoki Kyoto University

research subject

The direct imaging of individual polymer chains would provide us indispensable information to understand the fundamental process of the polymer dynamics. In the current study, the conformation and segment of a single polymer chain are observed by the state-of-art fluorescence microscopy techniques, and the chain dynamics in the stress relaxation process and in an ultra-thin film is discussed.

Sato group

Molecular Mechanism of Micellization of Thermoresponsive Block Copolymers in Aqueous Solution

 

[ Leader ]	[ Member ]	[ Collaborator ]
Takahiro Sato Osaka University	Toshiyuki Shikata Osaka University	Shin-ichi Yusa University of Hyogo

research subject

Block copolymers comprising thermoresponsive and water-soluble blocks have potential applications as the drug delivery system, nano-reactor, etc. For such applications, the accurate characterization of the micelle as well as understanding of the micellization mechanism are prerequisite. In this research project, we investigate the intermolecular interaction of thermoresponsive block copolymers, like poly(N-isopropylacrylamide)-b-poly(N-vinyl-2-pyrrolidone), with water by dielectric dispersion and infrared absorption, and the micellar structure formed by the copolymers by light scattering to reveal the molecular mechanism of micellization.

Tanaka group

Polymer Dynamics at Interfaces with SolidSubstrates

 

[ Leader ]	[ Member ]
Keiji Tanaka Kyushu University	Hiroshi Morita Institute of Advanced Industrial Science and Technology

research subject

In this research project, the segmental motion of polymers at interfaces with inorganic solids will be studied. For example, the interfacial glass transition temperature of polymers and the depth dependence from the interface will be examined by time- and space-resolved fluorescence spectroscopy. In addition, chain conformation of polymers at the interfaces will be also examined and be combined with the information of the segmental dynamics. These experimental results will be directly compared with simulation results.

Takahashi group

Study on Structure and Dynamics of Ionic Liquids

 

[ Leader ]	[ Member ]
Yoshiaki Takahashi Kyushu University	Akihiko Takada Kyushu University

research subject

We have found that a typical ionic liquid, 1-butyl-3-methylimidazolium chloride（BmimCl）containing small amount of water shows abnormal viscosity increment when LiCl is dissolved and also shows shear thinning behavior. Structure and dynamics of BmimCl/water/LiCl system and other systems mixed with organics will be examined in this project.