arXiv subjects

Takashi Yasuda

Publications and source records attributed to Takashi Yasuda.

8 recordsLinked to original sources

arXiv2026

Partitioning Law of Polymer Chains into Flexible Polymer Networks

The equilibrium partitioning of linear polymer chains into flexible polymer networks is governed by intricate entropic constraints arising from the configurational degrees of freedom of both chains and networks; however, a quantitative understanding remains elusive. Using model hydrogels with precisely defined network structures, we experimentally demonstrate a universal law governing the partitioning of linear polymers into flexible polymer networks. We establish a label-free contactless method to measure the partition ratio, based on the increase in the osmotic pressure induced by the partitioning of the external polymer chains. Moreover, we reveal a universal law in which the partition ratio is determined solely by $R_g / l_\mathrm{cycle}$, where $R_g$ is the gyration radius of the polymer chain and $l_\mathrm{cycle}\equiv ξ^{-1/3}$ is the characteristic mesh size of the network, defined by the cycle rank $ξ$, i.e., the number density of elastically effective cycles.

cond-mat.soft↗

arXiv2026

Mode-Resolved Light Scattering Recovers Polymer Thermodynamics in Solutions with Trace Large-Mass Scatterers

Light scattering provides direct access to polymer conformations and thermodynamics. However, trace large-mass scatterers such as aggregates and nanobubbles form unavoidably in polymer solutions and dominate the scattered intensity, obscuring the intrinsic polymer signal. We demonstrate that resolving the static scattering intensity by molecular mobility cleanly separates the polymer and large-scatterer contributions. Applying this mode-resolved analysis to aqueous poly(ethylene glycol) solutions, we isolate the polymer scattering even when these scatterers account for more than 90 % of the total intensity. The resolved polymer intensity recovers the universal osmotic equation of state from the dilute to the semidilute regime over 288 to 358 K. This approach establishes a reliable basis for measuring the thermodynamics of interacting macromolecules in solutions where irreproducible large-mass scatterers have precluded quantitative analysis.

cond-mat.soft↗

arXiv2024

Polymer Network Diffusion in Charged Gels

The swelling kinetics of charged polymer gels reflect the complex competition among elastic, mixing, and ionic contributions. Here, we used dynamic light scattering to investigate the collective diffusion coefficient of model gels, whose polymer network structure was controlled so that the three contributions were comparable. We demonstrate that the collective diffusion coefficient stems from the sum of elastic, mixing, and ionic contributions, without evident cross-correlations. The significant ionic contribution conforms to the Donnan equilibrium, which explains equilibrium electrical potential gradients in biological systems.

cond-mat.soft↗

arXiv2023

Universality of Osmotic Equation of State in Star Polymer Solutions

We experimentally measure the osmotic pressures of linear polymers and three-, four-, and eight-arm star polymers in a good solvent via membrane osmometry. These results reveal that the osmotic equations of state in the star polymer solutions are universally described by the same scaling function that describes linear polymer solutions. This universality is achieved by canceling increasing overlap concentrations and decreasing osmotic pressure, owing to the increased arm number. We further clarify the molar mass and arm number dependencies of the gyration radius and interpenetration factor, ensuring universality in star polymer solutions.

cond-mat.soft↗

arXiv2022

Semidilute Principle for Gels

Polymer gels such as jellies and soft contact lenses are soft solids consisting of three-dimensional polymer networks swollen with a large amount of solvent. For approximately 80 years, the swelling of polymer gels has been described using the Flory--Huggins mean-field theory. However, this theory is problematic when applied to polymer gels with large solvent contents owing to the significant fluctuations in polymer concentration. In this study, we experimentally demonstrate the superiority of the semidilute scaling law over the mean-field theory for predicting the swelling of polymer gels. Using the semidilute scaling law, we experimentally determine the universal critical exponent $ν$ of the self-avoiding walk via swelling experiments on polymer gels. The experimentally obtained value $ν\simeq 0.589$ is consistent with the previously reported value of $ν\simeq 0.588$, which was obtained by precise numerical calculations. Furthermore, we theoretically derive and experimentally demonstrate a scaling law that governs the equilibrium concentrations. This scaling law contradicts the predictions made by de Gennes' $c^{*}$ theorem. A major deficiency of the $c^*$ theorem is that the network elasticity, which depends on the as-prepared state, is neglected. These findings reveal that the semidilute scaling law is a fundamental principle for accurately predicting and controlling the equilibrium swelling of polymer gels.

cond-mat.soft↗

arXiv2020

Universal equation of state describes osmotic pressure throughout gelation process

The equation of state of the osmotic pressure for linear-polymer solutions in good solvents is universally described by a scaling function. We experimentally measure the osmotic pressure of the gelation process via osmotic deswelling. We find that the same scaling function for linear-polymer solutions also describes the osmotic pressure throughout the gelation process involving both the sol and gel states. Furthermore, we reveal that the osmotic pressure of polymer gels is universally governed by the semidilute scaling law of linear-polymer solutions.

cond-mat.stat-mech↗

arXiv2006

Evidence for Novel Pairing State in Noncentrosymmetric Superconductor CePt3Si: 29Si-NMR Knight Shift Study

We report the measurements of the $^{29}$Si Knight shift $^{29}K$ on the noncentrosymmetric heavy-fermion compound CePt$_{3}$Si in which antiferromagnetism (AFM) with $T_{\rm N}=2.2$ K coexists with superconductivity (SC) with $T_{c}=0.75$ K. Its spin part $^{29}K_{\rm s}$, which is deduced to be $K_{\rm s}^{c}\ge 0.11$ and 0.16% at respective magnetic fields $H=2.0061$ and 0.8671 T, does not decrease across the superconducting transition temperature $T_{c}$ for the field along the c-axis. The temperature dependence of nuclear spin-lattice relaxation of $^{195}$Pt below $T_{c}$ has been accounted for by a Cooper pairing model with a two-component order parameter composed of spin-singlet and spin-triplet pairing components. From this result, it is shown that the Knight-shift data are consistent with the occurrence of the two-component order parameter for CePt$_{3}$Si.

cond-mat.supr-con↗

arXiv2005

Novel Pressure Phase Diagram of Heavy Fermion Superconductor CePt$_{3}$Si Investigated by ac Calorimetry

The pressure dependences of the antiferromagnetic and superconducting transition temperatures have been investigated by ac heat capacity measurement under high pressures for the heavy-fermion superconductor CePt$_3$Si without inversion symmetry in the tetragonal structure. The Néel temperature $T_{\rm N}$ = 2.2 K decreases with increasing pressure and becomes zero at the critical pressure $P_{\rm AF}$ $\simeq$ 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa. The pressure phase diagram of CePt$_3$Si is thus very unique and has never been reported before for other heavy fermion superconductors.

cond-mat.supr-con↗