Behavior of a polymer chain immersed in a binary mixture of solvents

Tomonari Sumi, Kazuhiko Kobayashi, Hideo Sekino

Research output: Contribution to journalArticle

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Abstract

The behavior of a polymer chain immersed in a binary solvent mixture is investigated via a single-polymer simulation using an effective Hamiltonian, where the solvent effects are taken into account through a density-functional theory for polymer-solvent admixtures. The liquid-liquid phase separation of the binary solvent mixture is modeled as that of a Lennard-Jones binary fluid mixture with weakly attractive interactions between the different components. Two types of energetic preferences of the polymer chain for the better solvent - (A) no preferential solvophilicity and (B) strong preferential solvophilicity - are employed as polymer-solvent interaction models. The radius of gyration and the polymer-solvent radial distribution functions are determined from the simulations of various molar fractions along an isotherm slightly above the critical temperature of the liquid-liquid phase separation. These quantities near the critical point conspicuously depend on the strength of the preferential solvophilicity. In the case where the polymer exhibits a strong preferential solvophilicity, a remarkable expansion of the polymer chain is observed near the critical point. On the other hand, in the case where the polymer has no preferential solvophilicity, no characteristic variation of the polymer conformation is observed even near the critical point. These results indicate that the expansion of a polymer chain enhances the local phase separation around it, acting as a nucleus of demixing in the vicinity of the critical point. This phenomenon in binary solvents near the liquid-liquid critical point is similar to the expansion of the polymer chain in one-component supercritical solvents near the liquid-vapor critical point, which we have reported [T. Sumi and H. Sekino J. Chem. Phys. 122, 194910 (2005)].

Original languageEnglish
Article number164904
JournalThe Journal of Chemical Physics
Volume127
Issue number16
DOIs
Publication statusPublished - 2007
Externally publishedYes

Fingerprint

Binary mixtures
binary mixtures
Polymers
polymers
critical point
Liquids
Phase separation
liquids
expansion
liquid phases
Hamiltonians
binary fluids
gyration
admixtures
radial distribution
Distribution functions
Density functional theory
Isotherms
Conformations
critical temperature

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Behavior of a polymer chain immersed in a binary mixture of solvents. / Sumi, Tomonari; Kobayashi, Kazuhiko; Sekino, Hideo.

In: The Journal of Chemical Physics, Vol. 127, No. 16, 164904, 2007.

Research output: Contribution to journalArticle

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