A practical density functional for polydisperse polymers
Department of Physics and Astronomy, University of Edinburgh, Kings Buildings
Mayfield Road, Edinburgh EH9 3JZ, UK
2 Departament de Física Fonamental, Universitat de Barcelona Av. Diagonal 647, 08028-Barcelona, Spain
Accepted: 23 May 2001
The Flory-Huggins equation of state for monodisperse polymers can be turned into a density functional by adding a square gradient term, with a coefficient fixed by appeal to RPA (random phase approximation). We present instead a model nonlocal functional in which each polymer is replaced by a deterministic, penetrable particle of known shape. This reproduces the RPA and square gradient theories in the small deviation and/or weak gradient limits, and can readily be extended to polydisperse chains. The utility of the new functional is shown for the case of a polydisperse polymer solution at coexistence in a poor solvent.
PACS: 61.20.Gy – Theory and models of liquid structure / 61.25.Hq – Macromolecular and polymer solutions; polymer melts; swelling / 64.75.+g – Solubility, segregation, and mixing; phase separation
© EDP Sciences, 2001