Single-chain collapse as a first-order transition: model for PEO in water
Materials Research Laboratory, University of California,
Santa Barbara, CA 93106, USA
2 Institut für Festkörperforschung, Forschungzentrum Jülich, Postfach 1913, D-52425 Jülich, Germany
3 Max-Planck-Institut für Polymerforschung - Postfach 3148, D-55021 Mainz, Germany
A simple model for polyethyleneoxide (PEO) is introduced and analyzed by Monte Carlo simulation. The occurrence of a solvation shell of PEO in water is modeled by two internal states of the monomers with an energy difference . In the solvated state the monomer excluded volume increases due to the bound water and prevents the collapse of the poor-solvent backbone. As a function of , which can be positive or negative, we find for a first-order collapse transition, while for the standard -point is recovered. Thus, if the solvation shell is accompanied by a lower internal energy ( as for PEO), the transition is always of first order.
PACS: 61.25.Hq – Macromolecular and polymer solutions; polymer melts / 64.70.-p – Phase equilibria, phase transitions, and critical points of specific substances / 64.75.+g – Solubility, segregation, and mixing
© EDP Sciences, 1996