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Zhang H, Sundaresan S, Webb MA. Molecular Dynamics Investigation of Nanoscale Hydrophobicity of Polymer Surfaces: What Makes Water Wet? J Phys Chem B 2023. [PMID: 37043668 DOI: 10.1021/acs.jpcb.3c00616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
The wettability of a polymer surface─related to its hydrophobicity or tendency to repel water─can be crucial for determining its utility, such as for a coating or a purification membrane. While wettability is commonly associated with the macroscopic measurement of a contact angle between surface, water, and air, the molecular physics that underlie these macroscopic observations are not fully known, and anticipating the relative behavior of different polymers is challenging. To address this gap in molecular-level understanding, we use molecular dynamics simulations to investigate and contrast interactions of water with six chemically distinct polymers: polytetrafluoroethylene, polyethylene, polyvinyl chloride, poly(methyl methacrylate), Nylon-66, and poly(vinyl alcohol). We show that several prospective quantitative metrics for hydrophobicity agree well with experimental contact angles. Moreover, the behavior of water in proximity to these polymer surfaces can be distinguished with analysis of interfacial water dynamics, extent of hydrogen bonding, and molecular orientation─even when macroscopic measures of hydrophobicity are similar. The predominant factor dictating wettability is found to be the extent of hydrogen bonding between polymer and water, but the precise manifestation of hydrogen bonding and its impact on surface water structure varies. In the absence of hydrogen bonding, other molecular interactions and polymer mechanics control hydrophobic ordering. These results provide new insights into how polymer chemistry specifically impacts water-polymer interactions and translates to surface hydrophobicity. Such factors may facilitate the design or processing of polymer surfaces to achieve targeted wetting behavior, and presented analyses can be useful in studying the interfacial physics of other systems.
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Affiliation(s)
- Hang Zhang
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Sankaran Sundaresan
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Michael A Webb
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
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Tinti A, Giacomello A, Meloni S, Casciola CM. Classical nucleation of vapor between hydrophobic plates. J Chem Phys 2023; 158:134708. [PMID: 37031130 DOI: 10.1063/5.0140736] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
Abstract
In this work, an extended classical nucleation theory (CNT), including line tension, is used to disentangle classical and non-classical effects in the nucleation of vapor from a liquid confined between two hydrophobic plates at a nanometer distance. The proposed approach allowed us to gauge, from the available simulation work, the importance of elusive nanoscale effects, such as line tension and non-classical modifications of the nucleation mechanism. Surprisingly, the purely macroscopic theory is found to be in quantitative accord with the microscopic data, even for plate distances as small as 2 nm, whereas in extreme confinement ([Formula: see text] nm), the CNT approximations proved to be unsatisfactory. These results suggest how classical nucleation theory still offers a computationally inexpensive and predictive tool useful in all domains where nanoconfined evaporation occurs—including nanotechnology, surface science, and biology.
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Affiliation(s)
- Antonio Tinti
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, 00184 Rome, Italy
| | - Alberto Giacomello
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, 00184 Rome, Italy
| | - Simone Meloni
- Dipartimento di Scienze Chimiche e Farmaceutiche, Universitá degli Studi di Ferrara, 44121 Ferrara, Italy
| | - Carlo Massimo Casciola
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, 00184 Rome, Italy
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Tinti A, Camisasca G, Giacomello A. Structure and dynamics of water confined in cylindrical nanopores with varying hydrophobicity. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2021; 379:20200403. [PMID: 34455842 PMCID: PMC8403978 DOI: 10.1098/rsta.2020.0403] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/18/2021] [Indexed: 06/11/2023]
Abstract
We report a detailed study of the main structural and dynamical features of water confined in model Lennard-Jones nanopores with tunable hydrophobicity and finite length ([Formula: see text] Å). The generic model of cylindrical confinement used is able to reproduce the wetting features of a large class of technologically and biologically relevant systems spanning from crystalline nanoporous materials, to mesoporous silica and ion channels. The aim of this work is to discuss the influence of parameters such as wall hydrophobicity, temperature, and pore size on the structural and dynamical features of confined water. Our simulation campaign confirmed the existence of a core domain in which water displays bulk-like structural features even in extreme ([Formula: see text] Å) confinement, while dynamical properties were shown to depend non-trivially on the size and hydrophobicity of the pores. This article is part of the theme issue 'Progress in mesoscale methods for fluid dynamics simulation'.
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Affiliation(s)
- Antonio Tinti
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Rome, Italy
| | - Gaia Camisasca
- Dipartimento di Matematica e Fisica, Università Roma Tre, Rome, Italy
| | - Alberto Giacomello
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Rome, Italy
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Hydrophilic and Hydrophobic Effects on the Structure and Themodynamic Properties of Confined Water: Water in Solutions. Int J Mol Sci 2021; 22:ijms22147547. [PMID: 34299171 PMCID: PMC8304151 DOI: 10.3390/ijms22147547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/26/2021] [Accepted: 07/07/2021] [Indexed: 11/17/2022] Open
Abstract
NMR spectroscopy is used in the temperature range 180–350 K to study the local order and transport properties of pure liquid water (bulk and confined) and its solutions with glycerol and methanol at different molar fractions. We focused our interest on the hydrophobic effects (HE), i.e., the competition between hydrophilic and hydrophobic interactions. Nowadays, compared to hydrophilicity, little is known about hydrophobicity. Therefore, the main purpose of this study is to gain new information about hydrophobicity. As the liquid water properties are dominated by polymorphism (two coexisting liquid phases of high and low density) due to hydrogen bond interactions (HB), creating (especially in the supercooled regime) the tetrahedral networking, we focused our interest to the HE of these structures. We measured the relaxation times (T1 and T2) and the self-diffusion (DS). From these times, we took advantage of the NMR property to follow the behaviors of each molecular component (the hydrophilic and hydrophobic groups) separately. In contrast, DS is studied in terms of the Adam–Gibbs model by obtaining the configurational entropy (Sconf) and the specific heat contributions (CP,conf). We find that, for the HE, all of the studied quantities behave differently. For water–glycerol, the HB interaction is dominant for all conditions; water–methanol, two different T-regions above and below 265 K are observable, dominated by hydrophobicity and hydrophilicity, respectively. Below this temperature, where the LDL phase and the HB network develops and grows, with the times and CP,conf change behaviors leading to maxima and minima. Above it, the HB becomes weak and less stable, the HDL dominates, and hydrophobicity determines the solution.
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Dhattarwal HS, Remsing RC, Kashyap HK. Intercalation-deintercalation of water-in-salt electrolytes in nanoscale hydrophobic confinement. NANOSCALE 2021; 13:4195-4205. [PMID: 33586725 DOI: 10.1039/d0nr08163a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Intercalation-deintercalation of water-in-salt (WIS) electrolytes in nanoscale confinement is an important phenomenon relevant to energy storage and self-assembly applications. In this article, we use molecular simulations to investigate the effects of intersurface separation on the structure and free energy underlying the intercalation-deintercalation of the Li bis(trifluoromethane)sulfonimide ([Li][TFSI]) water-in-salt (WIS) electrolyte confined between nanoscale hydrophobic surfaces. We employ enhanced sampling to estimate the free energy profiles for the intercalation behaviour of WIS in confining sheets at several intersurface separations. We observe that the relative stability of the condensed and vapour phases of WIS in the confinement depends on the separation between the confining surfaces and the WIS concentration. We find that the critical separation at which the condensed and vapour phases are equally stable in confinement depends on the concentration of WIS. The relative height of the free energy barrier also strongly depends on the concentration of [Li][TFSI] inside the confined space, and we find that this concentration dependence can be attributed to changes in line tension. The process of deintercalation passes through vapour tube formation inside the confined space, and this process is initiated by vapour bubble formation. The size of the critical vapour tube required for spontaneous evaporation of WIS from the confinement is also found to depend on the intersurface separation and WIS concentration.
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Affiliation(s)
- Harender S Dhattarwal
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
| | - Richard C Remsing
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Hemant K Kashyap
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
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Klesse G, Tucker SJ, Sansom MSP. Electric Field Induced Wetting of a Hydrophobic Gate in a Model Nanopore Based on the 5-HT 3 Receptor Channel. ACS NANO 2020; 14:10480-10491. [PMID: 32673478 PMCID: PMC7450702 DOI: 10.1021/acsnano.0c04387] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/16/2020] [Indexed: 05/14/2023]
Abstract
In this study we examined the influence of a transmembrane voltage on the hydrophobic gating of nanopores using molecular dynamics simulations. We observed electric field induced wetting of a hydrophobic gate in a biologically inspired model nanopore based on the 5-HT3 receptor in its closed state, with a field of at least ∼100 mV nm-1 (corresponding to a supra-physiological potential difference of ∼0.85 V across the membrane) required to hydrate the pore. We also found an unequal distribution of charged residues can generate an electric field intrinsic to the nanopore which, depending on its orientation, can alter the effect of the external field, thus making the wetting response asymmetric. This wetting response could be described by a simple model based on water surface tension, the volumetric energy contribution of the electric field, and the influence of charged amino acids lining the pore. Finally, the electric field response was used to determine time constants characterizing the phase transitions of water confined within the nanopore, revealing liquid-vapor oscillations on a time scale of ∼5 ns. This time scale was largely independent of the water model employed and was similar for different sized pores representative of the open and closed states of the pore. Furthermore, our finding that the threshold voltage required for hydrating a hydrophobic gate depends on the orientation of the electric field provides an attractive perspective for the design of rectifying artificial nanopores.
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Affiliation(s)
- Gianni Klesse
- Department
of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
- Clarendon
Laboratory, Department of Physics, University
of Oxford, Oxford OX1 3PU, United Kingdom
| | - Stephen J. Tucker
- Clarendon
Laboratory, Department of Physics, University
of Oxford, Oxford OX1 3PU, United Kingdom
- OXION
Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Mark S. P. Sansom
- Department
of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
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Hussain S, Haji-Akbari A. Studying rare events using forward-flux sampling: Recent breakthroughs and future outlook. J Chem Phys 2020; 152:060901. [DOI: 10.1063/1.5127780] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Sarwar Hussain
- Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520, USA
| | - Amir Haji-Akbari
- Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520, USA
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Playing the long game wins the cohesion-adhesion rivalry. Proc Natl Acad Sci U S A 2019; 116:23874-23876. [PMID: 31659047 DOI: 10.1073/pnas.1916911116] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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9
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Abstract
Nanoscale confinement has a strong effect on the phase behavior of water. Studies in the last two decades have revealed a wealth of novel crystalline and quasicrystalline structures for water confined in nanoslits. Less is known, however, about the nature of ice-liquid coexistence in extremely nanoconfined systems. Here, we use molecular simulations to investigate the ice-liquid equilibrium for water confined between two nanoscopic disks. We find that the nature of ice-liquid phase coexistence in nanoconfined water is different from coexistence in both bulk water and extended nanoslits. In highly nanoconfined systems, liquid water and ice do not coexist in space because the two-phase states are unstable. The confined ice and liquid phases coexist in time, through oscillations between all-liquid and all-crystalline states. The avoidance of spatial coexistence of ice and liquid originates on the non-negligible cost of the interface between confined ice and liquid in a small system. It is the result of the small number of water molecules between the plates and has no analogue in bulk water.
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Affiliation(s)
- Noah Kastelowitz
- Department of Chemistry , The University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
| | - Valeria Molinero
- Department of Chemistry , The University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
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Shrivastav G, Remsing RC, Kashyap HK. Capillary evaporation of the ionic liquid [EMIM][BF4] in nanoscale solvophobic confinement. J Chem Phys 2018; 148:193810. [PMID: 30307173 DOI: 10.1063/1.5010259] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Gourav Shrivastav
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Richard C. Remsing
- Institute for Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Hemant K. Kashyap
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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