Statistical description of co-nonsolvency suppression at high pressures

Budkov, Yu. A.; Kolesnikov, A. L.

doi:10.1039/c7sm01637a

Cited by 19 publications

(28 citation statements)

References 53 publications

(83 reference statements)

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“…There, the polymers can be used as carriers and allow a controlled release of a variety of substances, such as drugs, fertilizers, herbicides, or nanoparticles. − Besides the main application as a carrier, thermoresponsive gels (partially) based on PNVCL are also applied in (bio)analytics, , catalysis, , and in a synergetic use with nanoparticles. ,, The thermoresponsiveness even allows mimicking a biopolymer/protein-like behavior . Compared to other thermoresponsive polymers, for example, the well-studied poly( N -isopropylacrylamide) (PNIPAM), ,− PNVCL shows favorable toxicological and ecological properties because it is not decomposed into small, potentially carcinogenic amide derivatives upon hydrolysis, making it a viable option especially for medical applications.…”

Section: Introductionmentioning

confidence: 99%

Cumulative Submillisecond All-Atom Simulations of the Temperature-Induced Coil-to-Globule Transition of Poly(N-vinylcaprolactam) in Aqueous Solution

et al. 2020

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Poly(N-vinylcaprolactam) (PNVCL) polymers are stimuli-responsive and change their conformation in aqueous solutions upon changes in salt concentration, concentration of organic solvents, or temperature, making these molecules highly interesting for tailored release of drugs or fabrication of sensors or actuators. At lower critical solution temperature (LCST), PNVCL chains undergo a transition from a coil to a globule and become insoluble. In contrast to other polymers, however, PNVCL has received much less attention as to elucidating driving forces of its coil-to-globule transition at an atomistic level. Here, we show by a combined computational and experimental study that upon temperature increase, PNVCL chains dissolved in water experience an increase of intramolecular interactions between C3 and C4 of the caprolactam ring. Therefore, more favorable cavity formation energies and the increase of intramolecular interactions outweigh the loss in polar and hydrophobic solvation, and the loss of configurational entropy in the coil-to-globule transition and, thus, may be considered driving forces of the polymer’s collapse at LCST. These results are based on molecular dynamics simulations of in total 600 μs length and transition (free) energy computations that have been validated internally and against experimental data. We systematically tested the influence of the polymer’s length, concentration, tacticity, of the thermodynamic ensemble, and of the water model. Tacticity was found to be most influential, with atactic polymers showing the strongest tendency to collapse. The presented approach should be applicable to scrutinize at the atomistic level the impact of, for example, ion and polymer dispersity on the coil-to-globule transition of PNVCL, and the LCST behavior of other polymers.

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Section: Introductionmentioning

confidence: 99%

Cumulative Submillisecond All-Atom Simulations of the Temperature-Induced Coil-to-Globule Transition of Poly(N-vinylcaprolactam) in Aqueous Solution

et al. 2020

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“…50,51 Driven by increasing interest in cononsolvency and the action of mixed solutes on the polymer structure, a whole body of mean-field theories has been developed especially for the description of the coil-to-globule transition in mixed solvents. 26,27,[52][53][54][55][56][57][58] Recently, we have developed a thermodynamic approach for neutral polymers (such as PNIPAM, or neutral ELPs) within the framework of preferential binding, 8,59 which helps interpreting the salt-specific thermodynamic fingerprints of cosolute-polymer interactions. 60 A similar model was used and extended to include non-specific screening effects for weakly charged polymers.…”

Section: Introductionmentioning

confidence: 99%

Tuning the collapse transition of weakly charged polymers by ion-specific screening and adsorption

2018

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The experimentally observed swelling and collapse response of weakly charged polymers to the addition of specific salts displays quite convoluted behavior that is not easy to categorize. Here we use a minimalistic implicit solvent / explicit salt simulation model with a focus on ion-specific interactions between ions and a single weakly charged polyelectrolyte to qualitatively explain the observed effects. In particular, we demonstrate ion-specific screening and bridging effects cause collapse at low salt concentrations whereas the same strong ion-specific direct interactions drive re-entrant swelling at high concentrations. Consistently with experiments, a distinct salt concentration at which the salting-out power of anions inverts from the reverse to direct Hofmeister series is observed. At this, so called isospheric point, the ion-specific effects vanish. Furthermore, with additional simplifying assumptions, an ion-specific mean-field model is developed for the collapse transition which quantitatively agrees with the simulations. Our work demonstrates the sensitivity of the structural behavior of charged polymers to the addition of specific salt and shall be useful for further guidance of experiments.

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“…In this approach, by looking at capillary forces at the nanograin level, sorption-induced deformation at the nanoscale such as nonaffine local deformation was discussed in detail. However, for nanoporous polymers with relatively large deformation, like those considered in the present work, the impact of deformation on the sorption process cannot be neglected as the pores of the deformed polymers lead to a new adsorption energy landscape [45][46][47] . The change of energy landscape can even lead to decrease of sorption amount upon adsorption, which is termed as 'negative gas adsorption' 47,48 .…”

Section: Introductionmentioning

confidence: 99%

A Poromechanical Model for Sorption Hysteresis in Nanoporous Polymers

et al. 2020

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Sorption hysteresis in nanoporous polymer is an intriguing phenomenon that involves coupling between sorption and deformation. Based on the mechanism revealed at the microscopic level using molecular simulation, a poromechanical model is developed capturing all relevant physics and yielding a quantitative description. In this model, the coupling between sorption and deformation is described by a poromechanics framework. More in detail, an upscaling process from the molecular mechanism is implemented to model the hysteresis through the state change of each element upon deformation. We provide two solutions of the model, a numerical one based on the finite element method and an analytical one based on uniform strain assumption. The results from both solutions agree well with the molecular simulation and experimental results, therefore capturing and describing adequately sorption hysteresis. The developed model illustrates that water forms different structural distributions upon adsorption and desorption. A parametric study shows that sorption hysteresis is influenced by material properties. We find that a softer material with stronger adsorbent-adsorbate interaction tends to exhibit more profound sorption hysteresis. The developed model, which relies on the concepts of sorption-deformation coupling and multi-scale modeling from atomistic simulations to domain dependent theory, paves the way for a new direction of modeling sorption hysteresis.

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Statistical description of co-nonsolvency suppression at high pressures

Cited by 19 publications

References 53 publications

Cumulative Submillisecond All-Atom Simulations of the Temperature-Induced Coil-to-Globule Transition of Poly(N-vinylcaprolactam) in Aqueous Solution

Cumulative Submillisecond All-Atom Simulations of the Temperature-Induced Coil-to-Globule Transition of Poly(N-vinylcaprolactam) in Aqueous Solution

Tuning the collapse transition of weakly charged polymers by ion-specific screening and adsorption

A Poromechanical Model for Sorption Hysteresis in Nanoporous Polymers

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