arXiv subjects

Yutaka Oya

Publications and source records attributed to Yutaka Oya.

5 recordsLinked to original sources

arXiv2025

Self-Consistent Field Theory for Semiflexible Gaussian Chain Model

Self-consistent field theory (SCFT) is one of the useful methods to simulate phase separated structures of multi-component polymer systems. In this article, we propose an SCFT for semiflexible polymer melts, where the basic equations for the SCFT are derived by introducing a bending stiffness into a flexible Gaussian bead-spring model and taking its continuous limit. Our SCFT is described by a coupled modified diffusion equations for the statistical weight of the chain conformation (path integral), which is a perturbation to semiflexible chains from the flexible Gaussian chain model. Using our modified diffusion equations, we investigated the influences of the bending stiffness on the conformations of symmetric semiflexible diblock copolymer in a strongly segregated lamellar structures and on the order-disorder transition.

cond-mat.soft↗

arXiv2020

Molecular dynamics simulation for cross-linking processes and material properties of epoxy resins with the first principle calculation combined with global reaction route mapping algorithms

Herein, epoxy resin is cured by coupling quantum chemical (QC) calculations with molecular dynamics (MD) simulations that enable parameter-free prediction of material characteristics. A polymer network is formed by the reaction between base resin and curing agent. The reaction uses activation energy and heat of formation data obtained by first-principle calculations coupled with global reaction route mapping (GRRM) algorithms. Density, glass transition temperature, Young's modulus, and curing conversion is used to validate the procedure. Experimental and simulation results indicate that base resin with multi-functional reaction groups increases glass-transition temperature and Young's modulus because of cross-linked formations at the molecular scale.

cond-mat.soft↗

arXiv2014

Onsager's Variational Principle for the Dynamics of a Vesicle in a Poiseuille Flow

We propose a systematic formulation of the migration behaviors of a vesicle in a Poiseuille flow based on Onsager's variational principle. Our model is described by a combination of the phase field theory for the vesicle and the hydrodynamics for the flow field. The time evolution equations for the phase field of the vesicle and the flow field are derived based on the Onsager's principle, where the dissipation functional is composed of viscous dissipation of the flow field, bending energy of the vesicle and the friction between the vesicle and the flow field. We performed a series of simulations on 2-dimensional systems by changing the bending elasticity of the membrane, and observed 3 types of steady states, i.e. those with bullet, snaking, and slipper shapes. We show that the transitions among these steady states can be quantitatively explained with use of the Onsager's principle, where the dissipation functional is dominated by the contribution from the friction between the vesicle and the flow field.

cond-mat.soft↗

arXiv2014

Soft Confinement for Polymer Solutions

As a model of soft confinement for polymers, we investigated equilibrium shapes of a flexible vesicle that contains a phase-separating polymer solution. To simulate such a system, we combined the phase field theory (PFT) for the vesicle and the self-consistent field theory (SCFT) for the polymer solution. We observed a transition from a symmetric prolate shape of the vesicle to an asymmetric pear shape induced by the domain structure of the enclosed polymer solution. Moreover, when a non-zero spontaneous curvature of the vesicle is introduced, a re-entrant transition between the prolate and the dumbbell shapes of the vesicle is observed. This re-entrant transition is explained by considering the competition between the loss of conformational entropy and that of translational entropy of polymer chains due to the confinement by the deformable vesicle. This finding is in accordance with the recent experimental result reported by Terasawa, et al.

physics.bio-ph↗

arXiv2010

Deformation of Equilibrium Shape of a Vesicle Induced by Injected Flexible Polymers

Using field theoretic approach, we study equilibrium shape deformation of a vesicle induced by the presence of enclosed flexible polymers, which is a simple model of drug delivery system or endocytosis. To evaluate the total free energy of this system, it is necessary to calculate the bending elastic energy of the membrane, the conformation entropy of the polymers and their interactions. For this purpose, we combine phase field theory for the membrane and self-consistent field theory for the polymers. Simulations on this coupled model system for axiosymmetric shapes show a shape deformation of the vesicle induced by introducing polymers into it. We examined the dependence of the stability of the vesicle shape on the chain length of the polymers and the packing ratio of the vesicle. We present a simple model calculation that shows the relative stability of the prolate shape compared to the oblate shape.

cond-mat.soft↗