Predicting the fluid-phase behavior of aqueous solutions of ELP (VPGVG) sequences using SAFT-VR.
Author(s)
Type
Journal Article
Abstract
The statistical associating fluid theory for potentials of variable range (SAFT-VR) is used to predict the fluid phase behavior of elastin-like polypeptide (ELP) sequences in aqueous solution with special focus on the loci of lower critical solution temperatures (LCSTs). A SAFT-VR model for these solutions is developed following a coarse-graining approach combining information from atomistic simulations and from previous SAFT models for previously reported relevant systems. Constant-pressure temperature-composition phase diagrams are determined for solutions of (VPGVG)n sequences + water with n = 1 to 300. The SAFT-VR equation of state lends itself to the straightforward calculation of phase boundaries so that complete fluid-phase equilibria can be calculated efficiently. A broad range of thermodynamic conditions of temperature and pressure are considered, and regions of vapor-liquid and liquid-liquid coexistence, including LCSTs, are found. The calculated phase boundaries at low concentrations match those measured experimentally. The temperature-composition phase diagrams of the aqueous ELP solutions at low pressure (0.1 MPa) are similar to those of types V and VI phase behavior in the classification of Scott and van Konynenburg. An analysis of the high-pressure phase behavior confirms, however, that a closed-loop liquid-liquid immiscibility region, separate from the gas-liquid envelope, is present for aqueous solutions of (VPGVG)30; such a phase diagram is typical of type VI phase behavior. ELPs with shorter lengths exhibit both liquid-liquid and gas-liquid regions, both of which become less extensive as the chain length of the ELP is decreased. The strength of the hydrogen-bonding interaction is also found to affect the phase diagram of the (VPGVG)30 system in that the liquid-liquid and gas-liquid regions expand as the hydrogen-bonding strength is decreased and shrink as it is increased. The LCSTs of the mixtures are seen to decrease as the ELP chain length is increased.
Date Issued
2017-08-08
Date Acceptance
2017-07-24
Citation
Langmuir, 2017, 33 (42), pp.11733-11745
ISSN
0743-7463
Publisher
American Chemical Society
Start Page
11733
End Page
11745
Journal / Book Title
Langmuir
Volume
33
Issue
42
Copyright Statement
© 2017 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Langmuir, after peer review and technical editing by the publisher. To access the final edited and published work see https://dx.doi.org/10.1021/acs.langmuir.7b02249
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/28789526
Grant Number
EP/E016340/1
EP/J014958/1
Subjects
Science & Technology
Physical Sciences
Technology
Chemistry, Multidisciplinary
Chemistry, Physical
Materials Science, Multidisciplinary
Chemistry
Materials Science
ELASTIN-LIKE POLYPEPTIDES
DIRECTIONAL ATTRACTIVE FORCES
CRITICAL SOLUTION TEMPERATURES
LIQUID-LIQUID IMMISCIBILITY
MONTE-CARLO SIMULATIONS
HIGH POLYMER-SOLUTIONS
CLOSED-LOOP LIQUID
EQUATION-OF-STATE
VAN-DER-WAALS
LCST BEHAVIOR
Chemical Physics
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2017-09-21