Structure and tension of the interface between dilute polymer solutions

I. Szleifer*, B. Widom

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

We treat a lattice model of phase separation in polymer solutions in mean-field (Flory) approximation, taking account of anisotropic biases in the chain conformations in the interface, as in an earlier theory of Helfand. Near the critical point of the phase separation those biases lead to a square-gradient contribution to the free-energy density that is of de Gennes' form, and thus to an interfacial tension that varies with polymerization index N and temperature distance below the critical point Tc - T as in the theories of Nose and of Vrij and Roebersen. In the scaling regime N→ ∞ and Tc - T→0 at fixed x = const N 1/2( T c - T) the surface tension σ is of the form N-1 Σ(x), with Σ(x) a scaling function that we display and that has the asymptotic behavior Σ(x) ∼ const x3/2 for x→0 and Σ(x) ∼ const x2 for x2→ ∞. The latter contrasts with the x5/2 found earlier when no account was taken of the chain-conformation biases. These biases are displayed as functions of location in the interface. On the concentrated-phase side of the interface the concentration of horizontal links is greater, and on the dilute-phase side it is less, than in a random chain.

Original languageEnglish (US)
Pages (from-to)7524-7534
Number of pages11
JournalThe Journal of Chemical Physics
Volume90
Issue number12
DOIs
StatePublished - 1989

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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