Chain organization and thermodynamics in micelles and bilayers. II. Model calculations

I. Szleifer*, A. Ben-Shaul, W. M. Gelbart

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

92 Scopus citations

Abstract

Based on the theory presented in part I (preceding paper) we calculate molecular and thermodynamic properties of model chains packed in micellar aggregates of three typical geometries: spheres, cylinders, and planar bilayers. Each possible conformation of a model chain is equivalent to a sequence of walks on a regular cubic lattice. The internal energy of a given conformation is proportional to the number of "kinks" (π/2 bond angles). The kink (gauche) energy measures the inherent flexibility of the chain. We calculate bond order parameter profiles for chains packed in aggregates of various curvature and radius, and find that in all cases the degree of conformational freedom increases from the chain head towards its end. The same qualitative behavior is observed for entirely flexible (zero kink energy) chains. This implies that the internal energy of the chain plays only a secondary role, compared to that of the packing constraints in determining chain conformational statistics in micellar aggregates. In accordance with this conclusion we also find that the geometry dependence of the conformational free energy is dominated by the entropic contribution. The differences between the minimal free energies of chains in different geometries are generally small. Yet, they may be comparable in magnitude to the changes associated with the surface ("opposing forces") contributions to the geometry dependence of the micelle's free energy.

Original languageEnglish (US)
Pages (from-to)3612-3620
Number of pages9
JournalThe Journal of Chemical Physics
Volume83
Issue number7
DOIs
StatePublished - Jan 1 1985

ASJC Scopus subject areas

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

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