Tsuyoshi Koga

We propose a computationally efficient method to simulate ordering processes in binary fluids with a long-range hydrodynamic interaction, and the results of a computer simulation of spinodal decomposition in binary fluids in three dimensions using this method are presented. A linear growth law of characteristic length scale l(t), namely l(t)\ensuremath{\sim}t, is observed in the very late scaling stage. The scaling function obtained is in good quantitative agreement with the experiments.

On the basis of results from a small-angle neutron scattering (SANS) study of aqueous solutions of a telechelic PNIPAM with octadecyl end groups, we developed a theoretical model of the self-assembly of this polymer in water as a function of temperature and concentration. This model leads us to the following description. In solutions of concentration 10 g L−1 kept between 10 and 20 °C, telechelic PNIPAMs (Mn = 22 200 g mol −1) associate in the form of flower micelles, containing about 12 polymer

The nonaffine transient network theory is used to study the time development of the shear and normal stresses under start-up shear flows in networks formed by self-assembled telechelic, hydrophobically modified water-soluble polymers. The initial slope, strain hardening, and overshoot of the shear stress are studied in detail in relation to the nonlinear tension-elongation curve of the elastically active chains in the network. The condition for the occurrence of strain hardening (upward deviatio

This paper studies the behavior of the normal stresses in associated networks composed of telechelic polymers under steady shear flow on the basis of a transient network theory. We numerically show that the first and second normal stress coefficients reveal thickening as a function of shear rate, and that the sign of the second normal stress coefficient changes depending on the nonlinearity in the chain tension, the dissociation rate of the associative groups from junctions, and the shear rate.

The isovolumetric contraction time is constant with gestation and fetal heart rate in normal pregnancy. In the presence of placental vascular disease a prolonged fetal isovolumetric contraction time predicts adverse outcome.

Herein, we developed thermoresponsive gelation systems of amphiphilic random copolymer micelles in water. To establish the design of micelle nanodomains for the physical gels, we synthesized random copolymers comprising hydrophilic poly(ethylene glycol) (average number of oxyethylene units = 4.5 or 8.5) and hydrophobic butyl or dodecyl groups. In water, the copolymers induced self-folding or intermolecular self-assembly to form unimer or multichain micelles, depending on their pendant structures

Structurally controlled hyperbranched poly(N-isopropylacrylamide)s (HB-PNIPAMs) having different branching densities were systematically synthesized, and their phase behavior, i.e., lower critical solution temperatures (LCSTs), in water was studied. The branching significantly affects LCSTs, and they decrease with an increase in the branching density. The origin of the experimental results was theoretically analyzed on the basis of the concept of cooperative hydration, which is the sequential fo

This paper proposes new design methodology, which enables a designer to generate a product behavior and topological structure based on step-by-step decomposition keeping their interdependency. In a development process of an industrial product, it is very important for designers to have enough consideration for the product behaviors. If some unexpected product-behaviors are overlooked, product-functions could be badly affected or catastrophically lost in the worst case. The authors show the effec