Division of Multidisciplinary Chemistry– Molecular Rheology –https://molrheo.kuicr.kyoto-u.ac.jp/en/

Assoc Prof
MATSUMIYA, Yumi(D Eng)

Assist Prof
SATO, Takeshi(D Eng)

Students
TOSAKI, Tomohiro (M1)
MATSUTO, Naoki (M1)
KAWAHIRA, Ayane (UG)

Scope of Research
Research focus is placed on the molecular origin ofrheological properties of various materials. Depending ontime and temperature, homogeneous polymeric materials
H[KLELWW\SLFDOIHDWXUHVRIJODVVUXEEHUDQGYLVFRXVÀXLG
while heterogeneous polymeric systems exhibit plasticity
in addition to these features. For basic understanding ofthese features, the molecular motion and structures at various scales are studied for polymeric systems in deformedstate. Rheological measurements are performed with various rheometers. Auto-correlation of the molecular orientation is also investigated with dynamic dielectric spectroscopy. Analysis of rheological and dielectric behavior
elucidates a new aspect of softmatter physics.

KEYWORDS
Rheology
Soft Matter

Dielectric Spectroscopy
Mesoscopic Model

Recent Selected Publications
Sato, T.; Matsumiya, Y.; Watanabe, H., Experimental Study of Phase Separation in Dynamically Asymmetric Unentangled Polymer Blend, J.
Chem. Phys., 157,   
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of Non-equilibrium Parameters, Nihon Reoroji Gakkaishi, 50,  
Sato, T., Modeling Techniques for the Rheology of Wormlike Micellar Solutions, Nihon Reoroji Gakkaishi, 50,  

TOPICS AND INTRODUCTORY COLUMNS OF LABORATORIESTopics
Rheo-Dielectric Behavior of UnentangledPoly(butylene oxide) under Steady Shear:
Preliminary Evaluation of Non-Equilibrium
Parameters at the Onset of Nonlinearity
For a type-A Rouse chain, a recent study derived ananalytical expression of its dielectric loss İ” under steadyshear in terms of the Rouse parameters, the spring strengthțWKHIULFWLRQFRH൶FLHQWȗ, and the mean-square Brownianforce intensity B, all being allowed to arbitrarily changewith the Weissenberg number Wi (i.e., shear rate multipliedby the longest relaxation time at equilibrium) and the latter
two having a tensorial form. Here, we have conducted arheo-dielectric test for a type-A unentangled melt, poly(butylene oxide) to measure İy” in the velocity gradient (y)direction as well as the viscosity Ș DQG WKH ¿UVW QRUPDOVWUHVVGL൵HUHQFHFRH൶FLHQWȌ1. Both dielectric relaxation
time and intensity were found to decrease on an increase ofWi up to the onset of rheological nonlinearity where Ș andȌ1 exhibited moderate thinning, but the dielectric relaxDWLRQPRGHGLVWULEXWLRQZDVQRWD൵HFWHGE\WKLVLQFUHDVHRI
Wi. Analyzing those İy”, ȘDQGȌ1 data on the basis of theabove expressions, we found that ț increases moderately
EXW WKH R൵GLDJRQDO FRPSRQHQWV RI ȗ remains negligibly
small on that increase of Wi. We also found that the diagonal components ȗxx (with x being the velocity direction)
and Byy hardly change but ȗyy decreases moderately. Theseresults serve as a starting point for deeper investigation ofț, ȗ, and B.

Experimental Study of Phase Separation in
Dynamically Asymmetric Unentangled Polymer Blend
We examined a phase separation process of a dynamically asymmetric blend of unentangled polyisoprene (PI) andpoly(4-ethylstyrene) (PC2St) exhibiting the upper criticalsolution temperature (UCST). PI having the type-A dipole
was the dielectrically active fast component, whereas
PC2St was the dielectrically inert slow component whose
dynamics can be detected by rheological measurements. To
precisely model the phase separation process, it is important to estimate the composition-dependence of the mobility
which is needed to describe the phase separation dynamics.
For that purpose, we conducted dielectric and rheological
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phase separation temperature. The temperature dependence
RIWKHIULFWLRQFRH൶FLHQWRIHDFKFRPSRQHQWZDVUHDVRQably expressed by the Williams-Landel-Ferry (WLF) equation. Extrapolating this dependence obtained for blends ofvarious compositions to the test temperature T* below thephase separation temperature, we were able to estimate theIULFWLRQFRH൶FLHQWRIWKHFKDLQDWT* as a function of the
FRPSRVLWLRQ7KLVIULFWLRQFRH൶FLHQWZDVWKHQXVHGWRGHWHUPLQHWKHPRELOLW\ȁGH¿QHGIRUWKHPDWHULDOÀX[HVDWT*.
The time-dependent Ginzburg-Landau (TDGL) equation
LQFRUSRUDWLQJWKLVȁZHOOGHVFULEHGWKHH[SHULPHQWDOO\REserved phase separation dynamics. In particular, the 2D
7'*/ VLPXODWLRQ ZLWK WKLV ȁ TXDOLWDWLYHO\ FDSWXUHG WKHphase-separated structure observed with the optical microscope as well as broad dielectric mode distribution of theblend at T*.

Figure 1. Changes of non-equilibrium parameters r’s with the Weissenberg number WiGH¿QHGZLWKUHVSHFWWRWKHORQJHVWYLVFRHODVWLFUHOD[DWLRQ
time in the LVE regime.

Figure 2. Schematic illustration of the experimental strategy to obtain themobility.

ICR ANNUAL REPORT, 2022

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