Molecular dynamics study of the intercalation and conformational transition of poly (N-vinyl caprolactam), a thermosensitive polymer in hydrated Na-montmorillonite

Camara, Moussa; Liao, Hualin; Xu, Jiafang; Zhang, Jun; Swai, Rogers

doi:10.1016/j.polymer.2019.121718

Cited by 15 publications

(8 citation statements)

References 55 publications

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“…Attempts to investigate the LCST behavior of PNVCL by all-atom MD simulations have been comparatively sparse, − and evaluations of the underlying thermodynamics, which is of great importance to fully understand the coil-to-globule transition, have been even rarer . Moreover, to our knowledge, there is no study in which, in a comparative manner, the behavior of PVP was probed under identical simulation conditions.…”

Section: Discussionmentioning

confidence: 99%

“…First studies on the thermoresponsiveness of PNVCL and the effect of the salt concentration and types on the LCST using MD simulations have been reported recently. ,− These include MD simulations at the coarse-grained, united-atom, and atomistic levels. , While indicating that modern MD simulations are suitable to investigate the coil-to-globule transition in PNVCL at the LCST, the majority of the published simulation data ,,− for thermoresponsive polymers describe the collapse at the LCST as a seemingly irreversible process because often no transition from the globule back to the coil is observed during the simulation time, which contradicts experimental observations; , notable exceptions exist. ,, Furthermore, a systematic assessment of the influence of polymer length, tacticity, and concentration on the thermoresponsiveness observed in MD simulations is rare. Finally, while most MD simulation studies evaluate structural parameters of the coil-to-globule transition, energetic determinants of the transition have only been computed for interactions between two isolated NVCL ( N -vinylcaprolactam) monomers so far …”

Section: Introductionmentioning

confidence: 99%

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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: Discussionmentioning

confidence: 99%

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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“…When r has a characteristic peak around 2–2.5 Å, it indicates that such hydrogen bonds exist in the system . The g ( r ) results of the two composite systems are shown in Figure .…”

Section: Resultsmentioning

confidence: 98%

Hydrogen Bonding Principle-Based Molecular Design of a Polymer Excipient and Impacts on Hydrophobic Drug Properties: Molecular Simulation and Experiment

et al. 2023

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Although some commercial excipients for improving the solubility of highly crystalline drugs are widely used, they still cannot cover all types of hydrophobic drugs. In this regard, with phenytoin as the target drug, related molecular structures of polymer excipients were designed. The optimal repeating units of NiPAm and HEAm were screened out through quantum mechanical simulation and Monte Carlo simulation methods, and the copolymerization ratio was also determined. Using molecular dynamics simulation technology, it was confirmed that the dispersibility and intermolecular hydrogen bonds of phenytoin in the designed copolymer were better than those in the commercial PVP materials. At the same time, the designed copolymers and solid dispersions were also prepared during the experiment, and the improvement of their solubility was confirmed, which is in accordance with the simulation predictions. The new ideas and simulation technology may be used for drug modification and development.

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“…From a viewpoint of computational cost, molecular dynamics (MD) simulation has been extensively used rather than quantum chemical calculation. Since the late 20th century, computational methods of clays have been developed including forcefields and crystal structures. − In most cases, however, only one kind of guest species has been the subject such as polymers, organoammonium ions, ionic liquids, cationic dyes, and metal complexes. ,− In other words, the nanocomposites containing more than one guest species have hitherto been limited to relatively simple systems. − Considering the recent trend of integration with experimental studies, the development of the computational method applicable to two guest species and following understanding of the interlayer structure with the Å-order resolution will uncover fundamental strategies for the on-demand design of novel layered materials, which has ever been attempted experimentally for decades.…”

Section: Introductionmentioning

confidence: 99%

Inhomogeneity of Organically Modified Montmorillonite Revealed by Molecular Dynamics Simulation

et al. 2021

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The modification of an interlayer of layered materials by intercalation with an organoammonium ion has been a promising method to control the polarity of the two-dimensional nanospace. Montmorillonite is one of the best-known examples, and the modification with octadecyltrimethylammonium ion (Mont-C18) results in adsorption of anthracene and pyrene together with specific excimer emission, while the nanostructure is yet to be uncovered at the molecular level because the gallery height is only ca. 27 Å. We, herein, investigated the nanostructure of this nanocomposite by molecular dynamics (MD) simulation, combined with analysis of molecular orientations against the Mont layer. The gallery height of Mont-C18 was well consistent with the experimental value, which was linearly increased along with the intercalation of anthracene. Anthracene was segregated on the Mont layer with its short and long molecular axes vertical in the early and late stages, respectively. In contrast, C18 was initially rather horizontal, forming the so-called pseudotrimolecular layer. Pushed out by anthracene, distribution and orientation of C18 were gradually changed: the third molecular layer was distinctly observed in the center of the interlayer in the early stage, and the orientation was changed to vertical in the late stage. Thus, the continuous increase in the gallery height is ascribed to soft response of C18 to the intercalation. Summarizing the abovementioned results, it was concluded that Å-order inhomogeneity is introduced in the interlayer by the intercalation of anthracene, which is significant in ideal design of the two-dimensional nanospace.

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Molecular dynamics study of the intercalation and conformational transition of poly (N-vinyl caprolactam), a thermosensitive polymer in hydrated Na-montmorillonite

Cited by 15 publications

References 55 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

Hydrogen Bonding Principle-Based Molecular Design of a Polymer Excipient and Impacts on Hydrophobic Drug Properties: Molecular Simulation and Experiment

Inhomogeneity of Organically Modified Montmorillonite Revealed by Molecular Dynamics Simulation

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