Closed miscibility loop phase behavior of polymer solutions

Oh, Suk Yung; Bae, Young Chan

doi:10.1016/j.polymer.2008.07.055

Cited by 22 publications

(19 citation statements)

References 23 publications

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“…Driving forces for phase separation at higher temperatures must be something that overcomes the opposite effect due to the entropy of mixing. Hirschfelder et al explained the demixing of aqueous solutions above LCST in terms of the formation of hydrogen bonds between unlike molecules at lower temperatures and the destruction of them at higher temperatures 6 ; the proposed mechanism has been widely used in constructing lattice models with LCST 7 8 9 . Continuum models with directional attractive interactions, based on the seminal work of Wertheim 10 11 , have been used to study closed-loop immiscibility 12 13 14 .…”

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confidence: 99%

Liquid–liquid phase separation of N-isopropylpropionamide aqueous solutions above the lower critical solution temperature

Mochizuki

Sumi

Koga

2016

Sci Rep

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We investigate driving forces of the liquid–liquid phase separation of N-isopropylpropionamide (NiPPA) aqueous solutions above the lower critical solution temperature using molecular dynamics simulations. Spontaneous phase separations of the model aqueous solution with a modified OPLS-AA force field are observed above the experimentally determined cloud point. The destabilization toward the phase separation is confirmed by temperature dependence of the long-wavelength limit of the concentration-concentration structure factor, the dominant component of which is found to be an increasing effective attraction between NiPPA molecules. At varying temperatures, the potentials of mean force (PMFs) between a pair of NiPPA molecules at infinite dilution are obtained and decomposed into the nonpolar and Coulombic contributions. The nonpolar contribution, arising essentially from molecular volume, promotes association of NiPPA molecules with increasing temperature while the Coulombic one antagonizes the association. Thus, our analysis leads to a conclusion that the driving force of thermally induced aggregation of NiPPA molecules is the temperature dependence of the nonpolar contribution in PMF between NiPPA molecules, not the temperature dependence of the number or strength of hydrogen bonds between NiPPA and water molecules.

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confidence: 99%

Liquid–liquid phase separation of N-isopropylpropionamide aqueous solutions above the lower critical solution temperature

Mochizuki

Sumi

Koga

2016

Sci Rep

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“…A number of researchers have suggested mathematical expressions for the interactions between polymer segments and solvents. [39][40][41][42] The temperature dependence of the interchange energy parameterẽ ij in a hydrogel system has a sigmoidal form, as noted by Lee and Bae. 41 Although their suggested expression provides good agreement with experimental data, it is semiempirical with five adjustable parameters required to represent a hydrogel system.…”

Section: Mixing Contributionmentioning

confidence: 91%

“…Mathematical representations of specific interactions, such as hydrogen bonding, play a crucial role in describing the swelling behavior of hydrogel systems. A number of researchers have suggested mathematical expressions for the interactions between polymer segments and solvents …”

Section: Thermodynamic Modelmentioning

confidence: 99%

Group contribution method for the swelling behavior of thermo‐responsive hydrogels

Yang

Bae

2017

J Polym Sci B Polym Phys

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A group contribution method is introduced to describe the swelling behavior of thermo‐sensitive hydrogel systems. The accuracy of group contribution calculations is strongly dependent on the choice of thermodynamic model. Therefore, we revise the modified double lattice (MDL) model and develop a new expression for the interaction energy parameter using the association theory of Sanchez to take into account complex polymer/solvent mixing. The net Helmholtz energy for a hydrogel is established by combining the revised MDL model and modified Flory–Rehner elastic model. Group parameters are generated by fitting to experimental swelling data from both homopolymer and copolymer gel systems. The effect of salt on the volume phase transition is modeled by introducing an additional salt‐specific parameter to investigate various stimuli‐response swelling behavior. Calculated swelling equilibria using the new group contribution method shows excellent agreement with experimental data and various stimuli‐response volume phase transitions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 455–463

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“…The de ij was replaced by de H ij À de S ij T in Eq. (8), where de H ij and de S ij are enthalpic and entropic energy contributions for the oriented interactions, respectively [30]. To incorporate a secondary lattice, e ij was replaced by e ij À DA sec;ij N ij in Eq.…”

Section: Oriented Interactionsmentioning

confidence: 99%

“…In previous studies [29,30], we developed a modified double lattice model (MDL) and successfully describe the liquid-liquid equilibria (LLE) with an upper critical solution temperature (UCST), lower critical solution temperature (LCST), and a closed miscibility loop phase behavior of binary polymer solutions. As a continuation of that effort, we present an extended MDL theory for multicomponent mixtures and compared our results to Monte Carlo simulation data for ternary systems.…”

Section: Introductionmentioning

confidence: 99%