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Pontoni D, DiMichiel M, Murphy BM, Honkimäki V, Deutsch M. Ordering of ionic liquids at a charged sapphire interface: Evolution with cationic chain length. J Colloid Interface Sci 2024; 661:33-45. [PMID: 38295701 DOI: 10.1016/j.jcis.2024.01.126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 01/09/2024] [Accepted: 01/18/2024] [Indexed: 02/27/2024]
Abstract
HYPOTHESIS Room Temperature Ionic Liquids (RTILs) bulk's molecular layering dominates their structure also at the RTIL/sapphire interface, increasing the layer spacing with the cationic alkyl chain length n. However, the negatively-charged sapphire surface compresses the layers, increases the layering range, and affects the intra-layer structure in yet unknown ways. EXPERIMENTS X-ray reflectivity (XR) off the RTIL/sapphire interface, for a broad homologous RTIL series 1-alkyl-3-methylimidazolium bis(trifluoromethansulfonyl)imide, hitherto unavailable for any RTIL. FINDINGS RTIL layers against the sapphire, exhibit two spacings: da and db. da is n-varying, follows the behavior of the bulk spacing but exhibits a downshift, thus showing significant layer compression, and over twofold polar slab thinning. The latter suggests exclusion of anions from the interfacial region due to the negative sapphire charging by x-ray-released electrons. The layering range is larger than the bulk's. db is short and near n-independent, suggesting polar moieties' layering, the coexistence mode of which with the da-spaced layering is unclear. Comparing the present layering with the bulk's and the RTIL/air interface's provides insight into the Coulomb and dispersion interaction balance dominating the RTIL's structure and the impact thereon of the presence of a charged solid interface.
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Affiliation(s)
- Diego Pontoni
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38043 Grenoble, France
| | - Marco DiMichiel
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38043 Grenoble, France
| | - Bridget M Murphy
- Institute of Experimental and Applied Physics, Kiel University, Kiel D-24098, Germany; Ruprecht-Haensel Laboratory, Kiel University, Kiel D-24118, Germany
| | - Veijo Honkimäki
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38043 Grenoble, France
| | - Moshe Deutsch
- Physics Dept. & Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan, Israel.
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Mechanistic insights into the crystallization of coamorphous drug systems. J Control Release 2023; 354:489-502. [PMID: 36646287 DOI: 10.1016/j.jconrel.2023.01.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 01/07/2023] [Accepted: 01/08/2023] [Indexed: 01/18/2023]
Abstract
In our previous study, the coamorphous formulation of lurasidone hydrochloride (LH) with saccharin (SAC) showed significantly enhanced dissolution and physical stability compared to crystalline/amorphous LH. However, the coamorphous system is still in amorphous state, and has the tendency to recrystallization, which will in turn result in the loss of above advantages. In this study, the crystallization kinetics under isothermal and non-isothermal conditions was investigated. Compared to amorphous LH, coamorphous LH-SAC showed 68.3-361.2 and 2.6-6.1 times lower crystallization rates in glassy state and supercooled liquid state, respectively. After co-amorphization, the addition of SAC changed the crystallization mechanism of amorphous LH from nucleation-controlled to diffusion-controlled manner. Amorphous LH followed the site-saturated nucleation, whereas the coamorphous system exhibited a fixed number of nuclei. The non-isothermal crystallization indicated amorphous LH and coamorphous LH-SAC showed two-dimensional (JMAEK 2) and three-dimensional (JMAEK 3) growth of nuclei, respectively. Furthermore, coamorphous LH-SAC exhibited higher molecular mobility and dynamic fragility (mD) than amorphous LH, which is kinetically unfavorable for its physical stability. However, from thermodynamic perspective, coamorphous LH-SAC had a higher configurational entropy, i.e., a higher entropy barrier for crystallization, which is beneficial to hinder its crystallization. Therefore, it was concluded that the higher configurational entropy rather than the molecular mobility was proposed to be responsible for its improved stability. In addition, molecular dynamics simulations with miscibility, radial distribution function and binding energy calculations suggested coamorphous components exhibited good miscibility and strong intermolecular interactions, which was also conductive to the enhancement in its stability. This study offers an in-depth understanding about the effect of the coformer on the crystallization kinetics of coamorphous systems, and points out the important contribution of the configurational entropy in stabilizing the coamorphous systems.
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Interfacial Forces in Free-Standing Layers of Melted Polyethylene, from Critical to Nanoscopic Thicknesses. Polymers (Basel) 2022; 14:polym14183865. [PMID: 36146008 PMCID: PMC9503058 DOI: 10.3390/polym14183865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/04/2022] [Accepted: 09/07/2022] [Indexed: 11/17/2022] Open
Abstract
Molecular dynamics simulations of ultrathin free-standing layers made of melted (373.15–673.15 K) polyethylene chains, which exhibit a lower melting temperature (compared to the bulk value), were carried out to investigate the dominant pressure forces that shape the conformation of chains at the interfacial and bulk liquid regions. We investigated layer thicknesses, tL, from the critical limit of mechanical stability up to lengths of tens of nm and found a normal distribution of bonds dominated by slightly stretched chains across the entire layer, even at large temperatures. In the bulk region, the contribution of bond vibrations to pressure was one order of magnitude larger than the contributions from interchain interactions, which changed from cohesive to noncohesive at larger temperatures just at a transition temperature that was found to be close to the experimentally derived onset temperature for thermal stability. The interchain interactions produced noncohesive interfacial regions at all temperatures in both directions (normal and lateral to the surface layer). Predictions for the value of the surface tension, γ, were consistent with experimental results and were independent of tL. However, the real interfacial thickness—measured from the outermost part of the interface up to the point where γ reached its maximum value—was found to be dependent on tL, located at a distance of 62 Å from the Gibbs dividing surface in the largest layer studied (1568 chains or 313,600 bins); this was ~4 times the length of the interfacial thickness measured in the density profiles.
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Shen P, Zhang C, Hu E, Pang Z, Gao Y, Qian S, Zhang J, Wei Y, Heng W. Gelation switch of polyamorphic indomethacin depending on the thermal procedure. Eur J Pharm Biopharm 2022; 177:249-259. [PMID: 35870760 DOI: 10.1016/j.ejpb.2022.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 07/13/2022] [Accepted: 07/18/2022] [Indexed: 11/29/2022]
Abstract
Amorphous indomethacin (IMC) prepared under different thermal procedures via melt quenching method showed significantly different dissolution behaviors. This study aims to investigate the influence of thermal procedures on the formation of IMC polyamorphism and to explore the mechanism for their different dissolution behaviors. Amorphous IMC samples were prepared by melting crystalline IMC under a series of temperatures (160-195 °C), respectively, followed by quenching in liquid nitrogen. Samples obtained under 170 °C exhibited bi-halo shapes at ∼15° and ∼26° (2θ), while the ones above 175 °C showed a single halo at ∼21° (2θ), suggesting amorphous IMC prepared under different thermal procedures probably have different local molecular arrangements. In comparison to crystalline IMC, amorphous IMC obtained under 170 °C showed significantly higher dissolution profiles with good dispersibility in aqueous medium, however, all amorphous IMC samples prepared above 175 °C demonstrated much lower dissolution with significant gelation, which seemed like a gelation switch existed for polyamorphic IMC when the preparation temperature was between 170 and 175 °C. Based on physicochemical characterizations, amorphous IMC prepared under 170 °C had higher surface free energy, more surficial hydrophilic groups and better wettability than the ones made above 175 °C. Molecular dynamics simulations revealed that the amorphous samples prepared below 170 °C had similar binding energy values in the range of 310.045-325.479 kcal/mol, while those prepared above 175 °C were significantly lower within 212.193-235.073 kcal/mol. Such binding energy difference might be responsible for their different local molecular arrangements after different thermal procedures. The current study deeply reminds us that the thermal procedure of preparation methods may significantly affect the physicochemical properties of amorphous materials, which should be paid special attention to the polymorphic selection during pharmaceutical development.
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Affiliation(s)
- Peiya Shen
- School of Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Chunfeng Zhang
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Enshi Hu
- School of Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Zunting Pang
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Yuan Gao
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Shuai Qian
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Jianjun Zhang
- School of Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China.
| | - Yuanfeng Wei
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China.
| | - Weili Heng
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China.
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González-Mijangos JA, Lima E, Guerra-González R, Ramírez-Zavaleta FI, Rivera JL. Critical Thickness of Free-Standing Nanothin Films Made of Melted Polyethylene Chains via Molecular Dynamics. Polymers (Basel) 2021; 13:3515. [PMID: 34685274 PMCID: PMC8538407 DOI: 10.3390/polym13203515] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 10/04/2021] [Accepted: 10/07/2021] [Indexed: 01/16/2023] Open
Abstract
The mechanical stability of nanothin free-standing films made of melted polyethylene chains was predicted via molecular dynamics simulations in the range of 373.15-673.15 K. The predicted critical thickness, tc, increased with the square of the temperature, T, with additional chains needed as T increased. From T = 373.15 K up to the thermal limit of stability for polyethylene, tc values were in the range of nanothin thicknesses (3.42-5.63 nm), which approximately corresponds to 44-55 chains per 100 nm2. The density at the center of the layer and the interfacial properties studied (density profiles, interfacial thickness, and radius of gyration) showed independence from the film thickness at the same T. The polyethylene layer at its tc showed a lower melting T (<373.15 K) than bulk polyethylene.
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Affiliation(s)
- José Antonio González-Mijangos
- Facultad de Ciencias Físico-Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia 58000, Mexico; (J.A.G.-M.); (F.I.R.-Z.)
| | - Enrique Lima
- Laboratorio de Fisicoquímica y Reactividad de Superficies (LaFReS), Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, Circuito Exterior S/N, CU, Del. Coyoacán, Ciudad de Mexico 04510, Mexico;
| | - Roberto Guerra-González
- Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, Morelia 58000, Mexico;
| | - Fernando Iguazú Ramírez-Zavaleta
- Facultad de Ciencias Físico-Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia 58000, Mexico; (J.A.G.-M.); (F.I.R.-Z.)
| | - José Luis Rivera
- Facultad de Ciencias Físico-Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia 58000, Mexico; (J.A.G.-M.); (F.I.R.-Z.)
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Arroyo-Valdez JA, Viramontes-Gamboa G, Guerra-Gonzalez R, Ramos-Estrada M, Lima E, Rivera JL. Cation folding and the thermal stability limit of the ionic liquid [BMIM +][BF 4 -] under total vacuum. RSC Adv 2021; 11:12951-12960. [PMID: 35423826 PMCID: PMC8697363 DOI: 10.1039/d1ra00741f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 03/29/2021] [Indexed: 12/28/2022] Open
Abstract
Molecular dynamics simulations reveal the behavior of the bimodal distribution of cation conformations (folded/unfolded) in ionic liquids based on alkylated imidazoles, such as [BMIM+][BF4 -]. The alkyl chains of the cations can fold and block interactions between the cations and anions, thereby reducing the cohesivity of the liquid. At room temperature, the folded conformations represent less than one-third of the total conformations. In contrast to the behavior observed during the thermal denaturation of proteins, in ionic liquids, the concentration of folded cations grows when the temperature increases. At the equimolar concentration, the system reaches the reported experimental temperature of thermal stability (similar to the thermal denaturation behavior). There is an outermost layer of cations at the interface that can tilt toward the interface and cover a layer of anions adsorbed at the interface. This interfacial conformation makes the system stable in transverse directions and unstable in the normal direction at temperatures in the region of thermal instability, limiting the rate of vaporization of neutral ion pairs, which are observed as rare events at temperatures as low as 773.15 K.
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Affiliation(s)
- J Alberto Arroyo-Valdez
- Facultad de Ciencias Físico-Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo Morelia Michoacán 58000 Mexico
| | - Gonzalo Viramontes-Gamboa
- Facultad de Ciencias Físico-Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo Morelia Michoacán 58000 Mexico
| | - Roberto Guerra-Gonzalez
- Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo Morelia Michoacán 58000 Mexico
| | - Mariana Ramos-Estrada
- Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo Morelia Michoacán 58000 Mexico
| | - Enrique Lima
- Laboratorio de Fisicoquímica y Reactividad de Superficies (LaFReS), Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México Circuito Exterior S/N, CU, Del. Coyoacán Ciudad de México Mexico
| | - José L Rivera
- Facultad de Ciencias Físico-Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo Morelia Michoacán 58000 Mexico
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Deutsch M, Magnussen OM, Haddad J, Pontoni D, Murphy BM, Ocko BM. Comment on "Bi-layering at ionic liquid surfaces: a sum - frequency generation vibrational spectroscopy - and molecular dynamics simulation-based study" by T. Iwahashi, T. Ishiyama, Y. Sakai, A. Morita, D. Kim and Y. Ouchi, Phys. Chem. Chem. Phys., 2020, 22, 12565. Phys Chem Chem Phys 2021; 23:5020-5027. [PMID: 33595568 DOI: 10.1039/d0cp04882h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This Comment raises several questions concerning the surface structure concluded in the paper referenced in the title. Specifically, that paper ignores previous experiments and simulations which demonstrate for the same ionic liquids depth-decaying, multilayered surface-normal density profiles rather than the claimed molecular mono- or bi-layers. We demonstrate that the claimed structure does not reproduce the measured X-ray reflectivity, which probes directly the surface-normal density profile. The measured reflectivities are found, however, to be well-reproduced by a multilayered density model. These results, and previous experimental and simulation results, cast severe doubt on the validity of the surface structure claimed in the paper referenced in the title.
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Affiliation(s)
- Moshe Deutsch
- Physics Department and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Olaf M Magnussen
- Institute for Experimental and Applied Physics and Ruprecht-Haensel Laboratory, Kiel University, 24118 Kiel, Germany
| | - Julia Haddad
- Physics Department and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Diego Pontoni
- Partnership for Soft Condensed Matter (PSCM), ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Bridget M Murphy
- Institute for Experimental and Applied Physics and Ruprecht-Haensel Laboratory, Kiel University, 24118 Kiel, Germany
| | - Benjamin M Ocko
- NSLS-II, Brookhaven National Laboratory, Upton, New York 11973, USA
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Teramoto T, Ohoyama H. Evidence of Direct Dissolution of CO 2 into the Ionic Liquid [C 4min] [NTf 2] during Their Initial Interaction. J Phys Chem B 2020; 124:8331-8339. [PMID: 32856912 DOI: 10.1021/acs.jpcb.0c05172] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ionic liquids (ILs) are known for their high ability to capture CO2. However, the mechanism of CO2 solubility into ILs during their initial interaction remains controversial. In this study, we analyzed the initial dissolution of CO2 into an IL 1-butyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide ([C4min] [NTf2]) by measuring its solubility using a combination of a molecular beam and a flowing liquid jet sheet beam (FJSB) and the King and Wells method (KW method). The temperature dependence of the initial dissolution probability indicates that the solubility of CO2 in the IL [C4min] [NTf2] increases with increasing temperature. This result is not consistent with what has been reported in an equilibrium state. The initial dissolution probability was well-fitted by the Vogel-Fulcher-Tammann (VFT) equation, which describes the dynamical cage structure in IL systems. We also find that the initial dissolution probability was correlated to the cage lifetime and correlation length. The simple model of CO2 dissolution into an IL with the cage model was implemented to explain the experimental results in this study. Our results indicate that the initial dissolution of CO2 into the IL corresponds to a direct solution and not an uptake process.
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Affiliation(s)
- Takahiro Teramoto
- Institute for Radiation Sciences, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Hiroshi Ohoyama
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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Dick EJ, Fouda AEA, Besley NA, Licence P. Probing the electronic structure of ether functionalised ionic liquids using X-ray photoelectron spectroscopy. Phys Chem Chem Phys 2020; 22:1624-1631. [PMID: 31894776 DOI: 10.1039/c9cp01297d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The charge distribution associated with individual components in functionalised ionic liquids (ILs) can be tuned by careful manipulation of the substituent groups incorporated into the ions. Here we use X-ray photoelectron spectroscopy to investigate the impact of substituent atoms on the electronic structure of similar imidazolium-based systems each paired with a common anion, [Tf2N]-. The experimental measurements revealed an unexpected variation in the charge density distribution within the IL cation when the oxygen atom in a poly-ether containing side chain is moved by just one atomic position. This surprising observation is supported by density functional theory calculations.
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Affiliation(s)
- Ejike J Dick
- School of Chemistry, The University of Nottingham, Nottingham NG7 2RD, UK. and The GSK Carbon Neutral Laboratory, The University of Nottingham Innovation Park, Triumph Road, Nottingham NG7 2TU, UK
| | - Adam E A Fouda
- School of Chemistry, The University of Nottingham, Nottingham NG7 2RD, UK.
| | - Nicholas A Besley
- School of Chemistry, The University of Nottingham, Nottingham NG7 2RD, UK.
| | - Peter Licence
- School of Chemistry, The University of Nottingham, Nottingham NG7 2RD, UK. and The GSK Carbon Neutral Laboratory, The University of Nottingham Innovation Park, Triumph Road, Nottingham NG7 2TU, UK
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Rivera JL, Douglas JF. Reducing uncertainty in simulation estimates of the surface tension through a two-scale finite-size analysis: thicker is better. RSC Adv 2019; 9:35803-35812. [PMID: 35528077 PMCID: PMC9074429 DOI: 10.1039/c9ra07058c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 10/29/2019] [Indexed: 12/21/2022] Open
Abstract
Recent simulation studies of the surface tension γ, and other properties of thin free-standing films, have revealed unexpected finite size effects in which the variance of the properties vary monotonically with the in-plane width of the films, complicating the extrapolation of estimates of film properties to the thermodynamic limit. We carried out molecular dynamics simulations to determine the origin of this phenomenon, and to address the practical problem of developing a more reliable methodology for estimating γ in the thermodynamic limit. We find that there are two distinct finite size effects that must be addressed in a finite size analysis of γ in thin films. The first finite size scale is the in-plane width of the films and the second scale is the simulation cell size in the transverse direction. Increasing the first scale enhances fluctuations in γ, measured by the standard deviation of their distribution, while increasing the second reduces γ fluctuations due to a corresponding increased ‘freedom’ of the film to fluctuate out of plane. We find that using progressively large simulation cells in the transverse direction, while keeping the film width fixed to an extent in which the full bulk liquid zone is developed, allows us to obtain a smooth extrapolation to the thermodynamic limit, enabling a reduction of the γ uncertainty to a magnitude on the order of 1% for systems having a reasonably large size, i.e., O (1 μm). The variance in the surface tension of systems under vapor/liquid equilibrium is strongly affected by the size of the interfacial area. Wider layers increase the variance, but these increments disappear as the interfacial area grows.![]()
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Affiliation(s)
- José L Rivera
- Laboratorio de Modelamiento y Simulación Molecular, Universidad Michoacana de San Nicolás de Hidalgo Morelia Michoacán 58000 Mexico
| | - Jack F Douglas
- Materials Science and Engineering Division, National Institute of Standards and Technology Gaithersburg Maryland 20899 USA
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Rivera JL, Douglas JF. Influence of film thickness on the stability of free-standing Lennard-Jones fluid films. J Chem Phys 2019; 150:144705. [DOI: 10.1063/1.5086284] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- José L. Rivera
- Laboratorio de Modelamiento y Simulación Molecular, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán 58000, Mexico
| | - Jack F. Douglas
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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