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The Role of Oxidation Pattern and Water Content in the Spatial Arrangement and Dynamics of Oxidized Graphene-Based Aqueous Dispersions. Int J Mol Sci 2022; 23:ijms232113459. [DOI: 10.3390/ijms232113459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 10/31/2022] [Accepted: 10/31/2022] [Indexed: 11/06/2022] Open
Abstract
In this work, we employ fully atomistic molecular dynamics simulations to elucidate the effects of the oxidation pattern and of the water content on the organization of graphene sheets in aqueous dispersions and on the dynamic properties of the different moieties at neutral pH conditions. Analysis of the results reveals the role of the oxidation motif (peripherally or fully oxidized flakes) in the tendency of the flakes to self-assemble and in the control of key structural characteristics, such as the interlayer distance between the sheets and the average size and the distribution of the formed aggregates. In certain cases, the results are compared to a pertinent experimental system, validating further the relevant computational models. Examination of the diffusional motion of the oxidized flakes shows that different degrees of spatial restriction are imposed upon the decrease in the water content and elucidates the conditions under which a motional arrest of the flakes takes place. At constant water content, the structural differences between the formed aggregates appear to additionally impart distinct diffusional characteristics of a water molecule. A detailed examination of the counterion dynamics describes their interaction with the oxidized flakes and their dependence on the water content and on the oxidation pattern, offering new insight into the expected electrical properties of the dispersions. The detailed information provided by this work will be particularly useful in applications such as molecular sieving, nanofiltration, and in cases where conductive membranes based on oxidized forms of graphene are used.
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Radhakrishnan K, Singh SP. Explicit characterization of counterion dynamics around a flexible polyelectrolyte. Phys Rev E 2022; 105:044501. [PMID: 35590562 DOI: 10.1103/physreve.105.044501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/04/2022] [Indexed: 06/15/2023]
Abstract
The article presents a comprehensive study of counterion dynamics around a generic linear polyelectrolyte chain with the help of coarse-grained computer simulations. The ion-chain coupling is discussed in the form of binding time, mean-square displacement (MSD) relative to the chain, local ion transport coefficient, and spatiotemporal correlations in the effective charge. We have shown that a counterion exhibits subdiffusive behavior 〈δR^{2}〉∼t^{δ}, δ≈0.9 w.r.t. chain's center of mass. The MSD of ions perpendicularly outward from the chain segment exhibits a smaller subdiffusive exponent compared to the one along the chain backbone. The effective diffusivity of ion is the lowest in chain's close proximity, extending up to the length-scale of radius of gyration R_{g}. Beyond R_{g} at larger distances, they attain diffusivity of free ion with a smooth cross-over from the adsorbed regime to the free ion regime. We have shown that the effective diffusivity drastically decreases for the multivalent ions, while the crossover length scale remains the same. Conversely, with increasing salt concentration the coupling-length scale reduces, while the diffusivity remains unaltered. The effective diffusivity of adsorbed-ion reveals an exponential reduction with electrostatic interaction strength. We further corroborate this from the binding time of ions on the chain, which also grows exponentially with the coupling strength of the ion-polymer duo. Moreover, the binding time of ions exhibits a weak dependence with salt concentration for the monovalent salt, while for multivalent salts the binding time decreases dramatically with concentration. Our work also elucidates fluctuations in the effective charge per site, where it exhibits strong negative correlations at short length-scales.
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Affiliation(s)
- Keerthi Radhakrishnan
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462 066, Madhya Pradesh, India
| | - Sunil P Singh
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462 066, Madhya Pradesh, India
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Hao QH, Xia G, Miao B, Tan HG, Niu XH, Liu LY. Morphological Response of a Spherical Polyelectrolyte Brush to Solvent Quality and Electrostatic Interaction Strength. Macromolecules 2018. [DOI: 10.1021/acs.macromol.8b01466] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Qing-Hai Hao
- College of Science, Civil Aviation University of China, Tianjin 300300, China
| | - Gang Xia
- College of Science, Civil Aviation University of China, Tianjin 300300, China
| | - Bing Miao
- College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hong-Ge Tan
- College of Science, Civil Aviation University of China, Tianjin 300300, China
| | - Xiao-Hui Niu
- College of Science, Civil Aviation University of China, Tianjin 300300, China
| | - Li-Yan Liu
- College of Science, Civil Aviation University of China, Tianjin 300300, China
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Karatasos K, Kritikos G. A microscopic view of graphene-oxide/poly(acrylic acid) physical hydrogels: effects of polymer charge and graphene oxide loading. SOFT MATTER 2018; 14:614-627. [PMID: 29265164 DOI: 10.1039/c7sm02305g] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this work we have examined in detail by means of fully atomistic molecular dynamics simulations, physical hydrogels formed by a polymer electrolyte, poly(acrylic acid), and graphene oxide, at two different charging states of the polymer and two different graphene oxide concentrations. It was found that variations of these parameters incurred drastic changes in general morphological characteristics of the composite materials, the degree of physical adsorption of polyelectrolyte chains onto the graphene oxide surface, the polymer dynamic response at local and global length scales, in the charge distributions around the components, and in the mobility of the counterions. All these microscopic features are expected to significantly affect macroscopic physical properties of the hydrogels, such as their mechanical responses and their electrical behaviors.
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Affiliation(s)
- Kostas Karatasos
- Laboratory of Physical Chemistry, Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
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Chremos A, Douglas JF. Counter-ion distribution around flexible polyelectrolytes having different molecular architecture. SOFT MATTER 2016; 12:2932-2941. [PMID: 26864861 DOI: 10.1039/c5sm02873f] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We explore the monovalent counter-ion distribution around flexible highly-charged polyelectrolytes with different molecular architectures (linear chains, stars, and unknotted and trefoil rings) using molecular dynamics simulations that include an explicit solvent that interacts with the polyelectrolyte. In particular, we find that the molecular topology influences the fraction of counter-ions transiently associating with the polyelectrolyte on a scale of the order of the chain segments, forming a "condensed" counter-ion interfacial layer. As with the hydrogen bonding of water to proteins and other polymers, the persistence time of these interfacial "bound" counter-ions is relatively short, O(1 ps), and we characterize the fluctuations in the number of the counter-ions populating the interfacial layer. We also find that the counter-ions are distributed in a non-uniform fashion on the polyelectrolyte backbone, forming dynamical clusters whose form and average size is sensitive to molecular architecture. In addition, we find that the residual bound counter-ions, not located in either the interfacial layer or the bulk solution, form a diffuse ionic cloud around the polyelectrolyte due to the uncompensated polyelectrolyte charge along the backbone. Generally charge valence strongly influences the extent of the diffuse counter-ion cloud, but in the case of monovalent counter-ions, we find that the size of the diffuse counter-ion cloud nearly coincides with the polyelectrolyte radius of gyration, independent of molecular topology.
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Affiliation(s)
- Alexandros Chremos
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
| | - Jack F Douglas
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
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Eghtesadi SA, Haso F, Kashfipour MA, Lillard RS, Liu T. Supramolecular Assembly of Poly(propyleneimine) Dendrimers Driven By Simple Monovalent Counterions. Chemistry 2015; 21:18623-30. [DOI: 10.1002/chem.201502852] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Indexed: 01/21/2023]
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Tauzin L, Shuang B, Kisley L, Mansur AP, Chen J, de Leon A, Advincula RC, Landes CF. Charge-dependent transport switching of single molecular ions in a weak polyelectrolyte multilayer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:8391-9. [PMID: 24960617 PMCID: PMC4216201 DOI: 10.1021/la5012007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The tunable nature of weak polyelectrolyte multilayers makes them ideal candidates for drug loading and delivery, water filtration, and separations, yet the lateral transport of charged molecules in these systems remains largely unexplored at the single molecule level. We report the direct measurement of the charge-dependent, pH-tunable, multimodal interaction of single charged molecules with a weak polyelectrolyte multilayer thin film, a 10 bilayer film of poly(acrylic acid) and poly(allylamine hydrochloride) PAA/PAH. Using fluorescence microscopy and single-molecule tracking, two modes of interaction were detected: (1) adsorption, characterized by the molecule remaining immobilized in a subresolution region and (2) diffusion trajectories characteristic of hopping (D ∼ 10(-9) cm(2)/s). Radius of gyration evolution analysis and comparison with simulated trajectories confirmed the coexistence of the two transport modes in the same single molecule trajectories. A mechanistic explanation for the probe and condition mediated dynamics is proposed based on a combination of electrostatics and a reversible, pH-induced alteration of the nanoscopic structure of the film. Our results are in good agreement with ensemble studies conducted on similar films, confirm a previously-unobserved hopping mechanism for charged molecules in polyelectrolyte multilayers, and demonstrate that single molecule spectroscopy can offer mechanistic insight into the role of electrostatics and nanoscale tunability of transport in weak polyelectrolyte multilayers.
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Affiliation(s)
- Lawrence
J. Tauzin
- Department
of Chemistry and Department of Electrical and Chemical Engineering, Rice University, Houston, Texas 77251, United States
| | - Bo Shuang
- Department
of Chemistry and Department of Electrical and Chemical Engineering, Rice University, Houston, Texas 77251, United States
| | - Lydia Kisley
- Department
of Chemistry and Department of Electrical and Chemical Engineering, Rice University, Houston, Texas 77251, United States
| | - Andrea P. Mansur
- Department
of Chemistry and Department of Electrical and Chemical Engineering, Rice University, Houston, Texas 77251, United States
| | - Jixin Chen
- Department
of Chemistry and Department of Electrical and Chemical Engineering, Rice University, Houston, Texas 77251, United States
| | - Al de Leon
- Department
of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Rigoberto C. Advincula
- Department
of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Christy F. Landes
- Department
of Chemistry and Department of Electrical and Chemical Engineering, Rice University, Houston, Texas 77251, United States
- E-mail:
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Pahari S, Roy S. Evidence and characterization of dynamic heterogeneity in binary mixtures of phosphoric acid and benzimidazole. J Chem Phys 2013; 139:154701. [PMID: 24160527 DOI: 10.1063/1.4824767] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We report here anomalous diffusions of components in mixtures of monomer of polybenzimidazole, i.e., 2-phenyl-1H,1'H-5,5'-bibenzo[d]imidazole (BI) and phosphoric acid (PA) from molecular dynamics simulations. We have observed initial drop and further increase in self-diffusion constant for both monomer molecule (BI) and PA with gradual increase in PA concentration. The origin of such anomalous diffusion is identified in this work, which happens to be the presence of dynamic heterogeneity in each component of the binary mixture. We characterized microscopic picture of dynamical heterogeneity by finding correlation between dynamical heterogeneity and structural arrangement among the components of the binary system. Different types of H-bonding arrangements in the BI-PA systems at different concentration of PA are observed. The stability of the H-bonded network consisting of different types of H-bonds between BI and PA in the system has been studied by calculating the lifetime of various H-bonds. The results indicate that there are fast and slow moving PA molecules in the mixtures because of coexistence of different types of hydrogen bonds among the components of the mixture.
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Affiliation(s)
- Swagata Pahari
- Physical Chemistry Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
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Kłos JS, Sommer JU. Coarse grained simulations of neutral and charged dendrimers. POLYMER SCIENCE SERIES C 2013. [DOI: 10.1134/s1811238213070023] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Tian WD, Ma YQ. Theoretical and computational studies of dendrimers as delivery vectors. Chem Soc Rev 2013; 42:705-27. [PMID: 23114420 DOI: 10.1039/c2cs35306g] [Citation(s) in RCA: 179] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
It is a great challenge for nanomedicine to develop novel dendrimers with maximum therapeutic potential and minimum side-effects for drug and gene delivery. As delivery vectors, dendrimers must overcome lots of barriers before delivering the bio-agents to the target in the cell. Extensive experimental investigations have been carried out to elucidate the physical and chemical properties of dendrimers and explore their behaviors when interacting with biomolecules, such as gene materials, proteins, and lipid membranes. As a supplement of the experimental techniques, it has been proved that computer simulations could facilitate the progress in understanding the delivery process of bioactive molecules. The structures of dendrimers in dilute solutions have been intensively investigated by monomer-resolved simulations, coarse-grained simulations, and atom-resolved simulations. Atomistic simulations have manifested that the hydrophobic interactions, hydrogen-bond interactions, and electrostatic attraction play critical roles in the formation of dendrimer-drug complexes. Multiscale simulations and statistical field theories have uncovered some physical mechanisms involved in the dendrimer-based gene delivery systems. This review will focus on the current status and perspective of theoretical and computational contributions in this field in recent years. (275 references).
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Affiliation(s)
- Wen-de Tian
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China
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Wu B, Liu Y, Li X, Mamontov E, Kolesnikov AI, Diallo SO, Do C, Porcar L, Hong K, Smith SC, Liu L, Smith GS, Egami T, Chen WR. Charge-Dependent Dynamics of a Polyelectrolyte Dendrimer and Its Correlation with Invasive Water. J Am Chem Soc 2013; 135:5111-7. [DOI: 10.1021/ja3125959] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bin Wu
- Department of Mechanical, Aerospace & Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Yun Liu
- The NIST Center for Neutron
Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6100, United States
- Department of Chemical Engineering, University of Delaware, Newark, Delaware 19716, United
States
| | | | | | | | | | | | - Lionel Porcar
- Institut Laue-Langevin, B.P. 156, F-38042 Grenoble CEDEX 9, France
| | | | | | - Li Liu
- Department of Mechanical, Aerospace & Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | | | - Takeshi Egami
- Department of Materials Science
and Engineering and Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1508,
United States
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Eleftheriou E, Karatasos K. Modeling the formation of ordered nano-assemblies comprised by dendrimers and linear polyelectrolytes: the role of Coulombic interactions. J Chem Phys 2013; 137:144905. [PMID: 23061863 DOI: 10.1063/1.4757666] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Models of mixtures of peripherally charged dendrimers with oppositely charged linear polyelectrolytes in the presence of explicit solvent are studied by means of molecular dynamics simulations. Under the influence of varying strength of electrostatic interactions, these systems appear to form dynamically arrested film-like interconnected structures in the polymer-rich phase. Acting like a pseudo-thermodynamic inverse temperature, the increase of the strength of the Coulombic interactions drive the polymeric constituents of the mixture to a gradual dynamic freezing-in. The timescale of the average density fluctuations of the formed complexes initially increases in the weak electrostatic regime reaching a finite limit as the strength of electrostatic interactions grow. Although the models are overall electrically neutral, during this process the dendrimer/linear complexes develop a polar character with an excess charge mainly close to the periphery of the dendrimers. The morphological characteristics of the resulted pattern are found to depend on the size of the polymer chains on account of the distinct conformational features assumed by the complexed linear polyelectrolytes of different length. In addition, the length of the polymer chain appears to affect the dynamics of the counterions, thus affecting the ionic transport properties of the system. It appears, therefore, that the strength of electrostatic interactions together with the length of the linear polyelectrolytes are parameters to which these systems are particularly responsive, offering thus the possibility for a better control of the resulted structure and the electric properties of these soft-colloidal systems.
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Affiliation(s)
- E Eleftheriou
- Physical Chemistry Laboratory, Chemical Engineering Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
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Karatasos K, Tanis I. Simulation of a Symmetric Binary Mixture of Charged Dendrimers Under Varying Electrostatic Interactions: Static and Dynamic Aspects. Macromolecules 2011. [DOI: 10.1021/ma2013282] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- K. Karatasos
- Physical Chemistry Laboratory, Chemical Engineering Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
| | - I. Tanis
- Physical Chemistry Laboratory, Chemical Engineering Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
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Kłos JS, Sommer JU. Simulations of Dendrimers with Flexible Spacer Chains and Explicit Counterions under Low and Neutral pH Conditions. Macromolecules 2010. [DOI: 10.1021/ma102055w] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- J. S. Kłos
- Leibniz Institute of Polymer Research Dresden e. V., 01069 Dresden, Germany
- Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
| | - J.-U. Sommer
- Leibniz Institute of Polymer Research Dresden e. V., 01069 Dresden, Germany
- Institute for Theoretical Physics, Technische Universität Dresden, 01069 Dresden, Germany
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Kłos JS, Sommer JU. Simulations of Terminally Charged Dendrimers with Flexible Spacer Chains and Explicit Counterions. Macromolecules 2010. [DOI: 10.1021/ma1003997] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- J. S. Kłos
- Leibniz Institute of Polymer Research Dresden e. V., 01069 Dresden, Germany
- Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
| | - J.-U. Sommer
- Leibniz Institute of Polymer Research Dresden e. V., 01069 Dresden, Germany
- Institute for Theoretical Physics, Technische Universität Dresden, 01069 Dresden, Germany
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Tian WD, Ma YQ. Complexation of a Linear Polyelectrolyte with a Charged Dendrimer: Polyelectrolyte Stiffness Effects. Macromolecules 2010. [DOI: 10.1021/ma901988m] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Wen-de Tian
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Yu-qiang Ma
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Laboratory of Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China
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