Relationship between polymer chain conformation and phase boundaries in a supercritical fluid
- Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States)
- Department of Chemical Engineering, University of Wisconsin, Madison, Wisconsin 53706 (United States)
We investigate the solvent density driven changes in polymer conformation and phase behavior that occur in a supercritical fluid, with a particular emphasis on conditions near the lower critical solution temperature (LCST) phase boundary. Using continuous space Monte Carlo simulations, the mean square end-to-end distance (R) and radius of gyration (R{sub g}) are calculated for a single chain with 20 Lennard-Jones segments in a monomeric solvent over a broad range of densities and temperatures. The chains collapse as temperature increases at constant pressure, or as density decreases at constant temperature. A minimum in R and R{sub g} occurs at a temperature slightly above the coil-to-globule transition temperature (C-GTT), where the chain adopts a quasi-ideal conformation, defined by the balance of binary attractive and repulsive interactions. Expanded ensemble simulations of finite-concentration polymer{endash}solvent mixtures reveal that the LCST phase boundary correlates well with the single chain C-GTT. At temperatures well above the LCST, the chain expands again suggesting an upper critical solution temperature (UCST) phase boundary above the LCST. {copyright} {ital 1997 American Institute of Physics.}
- DOE Contract Number:
- FG03-96ER14664
- OSTI ID:
- 554332
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 24 Vol. 107; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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