1
|
Li X, Wang Z, Wang Z, Yin Y, Jiang R, Zhang P, Li B. A novel microscopic origin of co-nonsolvency. SOFT MATTER 2025. [PMID: 40423567 DOI: 10.1039/d5sm00164a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2025]
Abstract
Co-nonsolvency presents a fundamental paradox in polymer physics where macromolecules undergo collapse or precipitation in mixed good solvents. Through investigations combining simulations of various binary good solvent systems of polymers, including single-chain and multi-chain of homopolymers and block copolymers, and ternary Flory-Huggins theoretical validation, we reveal that the competition between the enthalpy of the system and the mixing entropy of binary solvents results in the liquid-liquid phase separation (LLPS) of the better solvent (S-solvent) and the co-nonsolvency phenomenon. To reduce the enthalpy, the polymer and S-solvent tend to mix together to maximize their contact, which, however, is entropically unfavorable due to the localization of the S-solvent in the polymer domain. The LLPS of the S-solvent, where different chain segments share the localized S-solvent molecules, simultaneously lowers the enthalpy and reduces the loss of the mixing entropy. This sharing leads the chain in single-chain systems to be in a locally folding conformation with a size being much smaller than that of the ideal chain. In multi-chain systems, however, the sharing can be among segments from different chains, which causes chain condensation and hence an average chain size larger than its ideal value. Our study provides a novel mechanism for co-nonsolvency and may provide insights into the LLPS in other soft matter systems.
Collapse
Affiliation(s)
- Xingye Li
- Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071, China.
| | - Zhiyuan Wang
- Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071, China.
| | - Zheng Wang
- Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071, China.
| | - Yuhua Yin
- Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071, China.
| | - Run Jiang
- Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071, China.
| | - Pengfei Zhang
- State Key Laboratory for Advanced Fiber Materials, Center for Advanced Low-Dimension Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.
| | - Baohui Li
- Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071, China.
| |
Collapse
|
2
|
Li X, Wang Y, Zhang P. Theoretical investigation on the conformation of polymer brushes in mixtures of binary solvents. J Chem Phys 2025; 162:194903. [PMID: 40377197 DOI: 10.1063/5.0268339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2025] [Accepted: 04/26/2025] [Indexed: 05/18/2025] Open
Abstract
Polymer brushes are extensively used in various applications, such as antifouling coatings and biomedical sensors. Mixed solvents entail versatile regulations on the conformation of polymer brushes. The understanding of the conformation of polymer brushes in mixtures of two solvents, however, is far from mature. In this work, we develop a self-consistent field (SCF) theory and an Alexander-de Gennes (A-dG) theory to examine the chain conformation of polymer brushes in mixtures of two miscible solvents. We systematically investigate how the Flory-Huggins interaction parameters among the three components, the composition of the mixed solvent, the grafting density, and the chain length, influence the brush height and the density profiles of various species. Our calculations exhibit many non-trivial phenomena, such as the collapse of brushes in mixtures of two good solvents and the worsening of solvent quality when adding a good solvent to a poor solvent. The physical mechanisms of these intriguing phenomena are rationalized via the interplay among the chain conformation entropy, the mixing entropy of the two solvents, and the competition in the interactions among the three species. Quantitative comparison between the SCF and the A-dG theories demonstrates that the latter theory can qualitatively capture the variation trends of the brush height and the average concentrations of different species, while the former theory can provide more detailed descriptions on the density profiles of various species in the brush. Our results here not only exhibit the richness and complexity of polymer brushes in mixed solvents but also provide valuable principles for the rational design of stimuli-responsive brushes.
Collapse
Affiliation(s)
- Xiangyu Li
- State Key Laboratory of Advanced Fiber Materials, Center for Advanced Low-Dimension Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China
| | - Yajing Wang
- State Key Laboratory of Advanced Fiber Materials, Center for Advanced Low-Dimension Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China
| | - Pengfei Zhang
- State Key Laboratory of Advanced Fiber Materials, Center for Advanced Low-Dimension Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China
| |
Collapse
|
3
|
Zhang P, Wang Z, Wang ZG. Conformation Transition of a Homopolymer Chain in Binary Mixed Solvents. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c01896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Pengfei Zhang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Center for Advanced Low-Dimension Materials, College of Material Science and Engineering, Donghua University, Shanghai 201620, China
| | - Zheng Wang
- School of Physics, Nankai University, Tianjin 300071, China
| | - Zhen-Gang Wang
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| |
Collapse
|
4
|
Nothdurft K, Müller DH, Brands T, Bardow A, Richtering W. Enrichment of methanol inside pNIPAM gels in the cononsolvency-induced collapse. Phys Chem Chem Phys 2019; 21:22811-22818. [DOI: 10.1039/c9cp04383g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
From Raman, we determined an enrichment of methanol inside the polymer in the cononsolvency-induced collapse and donor-type hydrogen-bonding of methanol with pNIPAM.
Collapse
Affiliation(s)
- Katja Nothdurft
- Institute of Physical Chemistry
- RWTH Aachen University
- 52056 Aachen
- Germany
| | - David H. Müller
- Institute of Technical Thermodynamics
- RWTH Aachen University
- 52062 Aachen
- Germany
| | - Thorsten Brands
- Institute of Technical Thermodynamics
- RWTH Aachen University
- 52062 Aachen
- Germany
| | - André Bardow
- Institute of Technical Thermodynamics
- RWTH Aachen University
- 52062 Aachen
- Germany
| | - Walter Richtering
- Institute of Physical Chemistry
- RWTH Aachen University
- 52056 Aachen
- Germany
| |
Collapse
|
5
|
Budkov YA, Kolesnikov AL. Models of the Conformational Behavior of Polymers in Mixed Solvents. POLYMER SCIENCE SERIES C 2018. [DOI: 10.1134/s1811238218020030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
6
|
Dudowicz J, Douglas JF, Freed KF. Lattice theory of competitive binding: Influence of van der Waals interactions on molecular binding and adsorption to a solid substrate from binary liquid mixtures. J Chem Phys 2018; 149:044704. [PMID: 30068175 DOI: 10.1063/1.5040105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The reversible binding of molecules to surfaces is one of the most fundamental processes in condensed fluids, with obvious applications in the molecular separation of materials, chromatographic characterization, and material processing. Motivated in particular by the ubiquitous occurrence of binding processes in molecular biology and self-assembly, we have developed a lattice type theory of competitive molecular binding to solid substrates from binary mixtures of two small molecule liquids that interact between themselves by van der Waals forces in addition to exhibiting binding interactions with the solid surface. The derived theory, in contrast to previously existing theoretical frameworks, enables us to investigate the influence of van der Waals interactions on interfacial binding and selective molecular adsorption. For reference, the classic Langmuir theory of adsorption is recovered when all van der Waals interaction energies between the molecules in the bulk liquid phase and those on the surface are formally set to zero. Illustrative calculations are performed for the binding of molecules to a solid surface from pure liquids and from their binary mixtures. The properties analyzed include the surface coverage θ, the binding transition temperature Tbind, the individual surface coverages, θA and θC, and the relative surface coverages, σAC≡θA/θC or σCA≡θC/θA. The latter two quantities coincide with the degrees of adsorption directly determined from experimental adsorption measurements. The Langmuir theory is shown to apply formally under a wide range of conditions where the original enthalpies (Δh or ΔhA and ΔhC) and entropies (Δs or ΔsA and ΔsC) of the binding reactions are simply replaced by their respective "effective" counterparts (Δheff or ΔhAeff and ΔhCeff and Δseff or ΔsAeff and ΔsCeff), whose values depend on the strength of der Waals interactions and of the "bare" free energy parameters (Δh or ΔhA and ΔhC, and Δs or ΔsA and ΔsC). Numerous instances of entropy-enthalpy compensation between these effective free energy parameters follow from our calculations, confirming previous reports on this phenomenon obtained from experimental studies of molecular binding processes in solution.
Collapse
Affiliation(s)
- Jacek Dudowicz
- Department of Chemistry, The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - Jack F Douglas
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Karl F Freed
- Department of Chemistry, The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| |
Collapse
|
7
|
Fukai T, Shinyashiki N, Yagihara S, Kita R, Tanaka F. Phase Behavior of Co-Nonsolvent Systems: Poly( N-isopropylacrylamide) in Mixed Solvents of Water and Methanol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:3003-3009. [PMID: 29412671 DOI: 10.1021/acs.langmuir.7b03815] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Cloud points of poly( N-isopropylacrylamide) in aqueous mixed solvents, with methanol as the cosolvent, are experimentally measured for polymer concentrations varied up to as high as the weight fraction 0.25. They are shown to form closed loops on the ternary phase plane in the temperature region between 5 and 30 °C, and hence co-nonsolvency is complete. Miscibility loops shrink by cooling, or equivalently, they exhibit lower critical solution temperature behavior. For a fixed polymer concentration, there is a composition of the mixed solvent at which the cloud-point temperature takes the lowest value. This minimum cloud-point temperature composition of the mixed solvent turned out to be almost independent of the polymer concentration, at least within the measured dilute region below the weight fraction 0.25. On the basis of the assumption that the phase separation is closely related to the preferential adsorption of the solvents by hydrogen bonding, we employ a model solution of Flory-Huggins type, augmented with direct and cooperative polymer-solvent hydrogen bonds, to construct the ternary phase diagrams. Theoretical calculation of the spinodal curves is performed, and the results are compared with the obtained experimental cloud-point data. The effect of molecular volume of the cosolvent is also studied within the same theoretical framework. Possibility for a upper critical solution temperature co-nonsolvency to appear for cosolvents with larger molecular volume is discussed.
Collapse
Affiliation(s)
| | | | | | | | - Fumihiko Tanaka
- Department of Polymer Chemistry , Kyoto University , Katsura , Kyoto 615-8510 , Japan
| |
Collapse
|
8
|
Budkov YA, Kiselev MG. Flory-type theories of polymer chains under different external stimuli. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:043001. [PMID: 29271365 DOI: 10.1088/1361-648x/aa9f56] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this Review, we present a critical analysis of various applications of the Flory-type theories to a theoretical description of the conformational behavior of single polymer chains in dilute polymer solutions under a few external stimuli. Different theoretical models of flexible polymer chains in the supercritical fluid are discussed and analysed. Different points of view on the conformational behavior of the polymer chain near the liquid-gas transition critical point of the solvent are presented. A theoretical description of the co-solvent-induced coil-globule transitions within the implicit-solvent-explicit-co-solvent models is discussed. Several explicit-solvent-explicit-co-solvent theoretical models of the coil-to-globule-to-coil transition of the polymer chain in a mixture of good solvents (co-nonsolvency) are analysed and compared with each other. Finally, a new theoretical model of the conformational behavior of the dielectric polymer chain under the external constant electric field in the dilute polymer solution with an explicit account for the many-body dipole correlations is discussed. The polymer chain collapse induced by many-body dipole correlations of monomers in the context of statistical thermodynamics of dielectric polymers is analysed.
Collapse
Affiliation(s)
- Yu A Budkov
- Tikhonov Moscow Institute of Electronics and Mathematics, School of Applied Mathematics, National Research University Higher School of Economics, Moscow, Russia. Laboratory of NMR Spectroscopy and Numerical Investigations of Liquids, G.A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Ivanovo, Russia
| | | |
Collapse
|
9
|
Budkov YA, Kolesnikov AL. Statistical description of co-nonsolvency suppression at high pressures. SOFT MATTER 2017; 13:8362-8367. [PMID: 29116278 DOI: 10.1039/c7sm01637a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We present an application of Flory-type theory of a flexible polymer chain dissolved in a binary mixture of solvents to theoretical description of co-nonsolvency. We show that our theoretical predictions are in good quantitative agreement with the recently published MD simulation results for the conformational behavior of a Lennard-Jones flexible chain in a binary mixture of the Lennard-Jones fluids. We show that our theory is able to describe co-nonsolvency suppression through pressure enhancement to extremely high values recently discovered in experiments and reproduced by full atomistic MD simulations. By analysing the co-solvent concentration in the internal polymer volume at different pressure values, we speculate that this phenomenon is caused by the suppression of the co-solvent preferential solvation of the polymer backbone at the rather high pressure imposed. We show that when the co-solvent-induced coil-globule transition takes place, the entropy and enthalpy contributions to the solvation free energy abruptly decrease, while the solvation free energy remains continuous.
Collapse
Affiliation(s)
- Yu A Budkov
- Tikhonov Moscow Institute of Electronics and Mathematics, School of Applied Mathematics, National Research University Higher School of Economics, Tallinskaya St. 34, 123458 Moscow, Russia.
| | | |
Collapse
|
10
|
Dudowicz J, Douglas JF, Freed KF. Mixtures of two self- and mutually-associating liquids: Phase behavior, second virial coefficients, and entropy-enthalpy compensation in the free energy of mixing. J Chem Phys 2017; 147:064909. [PMID: 28810766 DOI: 10.1063/1.4996921] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The theoretical description of the phase behavior of polymers dissolved in binary mixtures of water and other miscible solvents is greatly complicated by the self- and mutual-association of the solvent molecules. As a first step in treating these complex and widely encountered solutions, we have developed an extension of Flory-Huggins theory to describe mixtures of two self- and mutually-associating fluids comprised of small molecules. Analytic expressions are derived here for basic thermodynamic properties of these fluid mixtures, including the spinodal phase boundaries, the second osmotic virial coefficients, and the enthalpy and entropy of mixing these associating solvents. Mixtures of this kind are found to exhibit characteristic closed loop phase boundaries and entropy-enthalpy compensation for the free energy of mixing in the low temperature regime where the liquid components are miscible. As discussed by Widom et al. [Phys. Chem. Chem. Phys. 5, 3085 (2003)], these basic miscibility trends, quite distinct from those observed in non-associating solvents, are defining phenomenological characteristics of the "hydrophobic effect." We find that our theory of mixtures of associating fluids captures at least some of the thermodynamic features of real aqueous mixtures.
Collapse
Affiliation(s)
- Jacek Dudowicz
- The James Franck Institute and the Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA
| | - Jack F Douglas
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Karl F Freed
- The James Franck Institute and the Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA
| |
Collapse
|