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Ma J, Haider OM, Chang CC, Grzesiak KA, Squires TM, Walker LM. Solvent Quality and Aggregation State of Asphaltenes on Interfacial Mechanics and Jamming Behavior at the Oil/Water Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:15238-15248. [PMID: 37862270 PMCID: PMC10620990 DOI: 10.1021/acs.langmuir.3c01890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 10/02/2023] [Indexed: 10/22/2023]
Abstract
The formation of highly stable water-in-oil emulsions results in complications in both upstream and downstream processing. Emulsion stability in these systems has been connected to the adsorption of surface-active asphaltenes that are assumed to form a rigidified film at the oil/water (o/w) interface. Full characterization of this behavior is needed to allow for engineered solutions for enhanced oil recovery. Interfacial properties, such as surface pressure and interfacial elasticity, are implicated in the stabilizing mechanism for these observed films. Asphaltenes are known to be interfacially active in both good solvents (aromatics) and poor solvents (high ratio of aliphatic to aromatic). However, due to inherent complexities present in asphaltene studies, the details of the mechanical properties of the interface remain poorly understood. Despite the widely accepted perception that asphaltenes form persistent rigid films at fluid-fluid interfaces, the connection between bulk solution properties and interfacial mechanics has not been resolved. Here, the effects of solvent quality on the interfacial properties of asphaltene dispersions are determined by using a well-defined asphaltene/solvent system. Interfacial rigidity is observed only under poor solvent conditions, while the good solvent system remains fluid-like. The interfacial rheology under good and poor solvent conditions is measured simultaneously with surface pressure measurements to track interfacial development. It is shown that surface pressure and dilatational modulus measurements are not indicators of whether an interface demonstrates rigid behavior under large compressions. Finally, conditions required for asphaltene-coated interfaces to exhibit the mechanical behavior associated with a rigidified interface are defined. This work provides a framework for quantifying the impact of the aggregation state of asphaltenes on the stability and mechanics at the o/w interface.
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Affiliation(s)
- Junchi Ma
- Department
of Chemical Engineering, Carnegie Mellon
University, Pittsburgh, Pennsylvania 15213, United States
| | - Olivia M. Haider
- Department
of Chemical Engineering, Carnegie Mellon
University, Pittsburgh, Pennsylvania 15213, United States
| | - Chih-Cheng Chang
- Department
of Chemical Engineering, University of California, Santa Barbara, California 93106, United States
| | | | - Todd M. Squires
- Department
of Chemical Engineering, University of California, Santa Barbara, California 93106, United States
| | - Lynn M. Walker
- Department
of Chemical Engineering, Carnegie Mellon
University, Pittsburgh, Pennsylvania 15213, United States
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Tazikeh S, Sayyad Amin J, Zendehboudi S, Shafiei A. Effects of asphaltene structure and polythiophene-coated magnetite nanoparticles on surface topography and wettability alteration of silica surface. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.118470] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Synergetic effect of asphaltenes extracted from polymer containing oil sludge and HPAM at water/toluene interface. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127572] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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4
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New innovations in pavement materials and engineering: A review on pavement engineering research 2021. JOURNAL OF TRAFFIC AND TRANSPORTATION ENGINEERING (ENGLISH EDITION) 2021. [DOI: 10.1016/j.jtte.2021.10.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Haji-Savameri M, Norouzi-Apourvari S, Irannejad A, Hemmati-Sarapardeh A, Schaffie M, Mosavi A. Experimental study and modelling of asphaltene deposition on metal surfaces with superhydrophobic and low sliding angle inner coatings. Sci Rep 2021; 11:16812. [PMID: 34413341 PMCID: PMC8377080 DOI: 10.1038/s41598-021-95657-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 07/22/2021] [Indexed: 02/07/2023] Open
Abstract
Inner coatings have emerged as a novel technique to prevent the deposition of paraffin, wax, scale, and corrosion of pipelines during oil production and transport. Few studies addressed this technique for preventing asphaltene deposition. In this study, two superhydrophobic inner coatings, including polytetrafluoroethylene (PTFE) coating and nanosilica coating, were fabricated on metal surfaces and the asphaltene deposition on these coated surfaces was examined. A model oil solution was prepared using asphaltene and heptol and the effect of static and dynamic flow states on the amount of asphaltene deposition on uncoated electrodes, PTFE coated electrodes, and nanosilica coated electrodes were investigated. The results showed that the PTFE coating is more effective in reducing asphaltene deposition than nanosilica coating. The PTFE coating could reduce 56% of the deposition in a static state and more than 70% in a dynamic state at an asphaltene concentration of 2000 ppm. For PTFE coating in a dynamic state, the deposition rate is negligible in long times. In addition, it was found that the type of flow state affects the asphaltene deposition kinetics. The results demonstrate that, in the static state, the nth-order kinetics model, and in the dynamic state, the double exponential models are in best agreement with the experimental data.
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Affiliation(s)
- Mohammad Haji-Savameri
- grid.412503.10000 0000 9826 9569Department of Petroleum Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
| | - Saeid Norouzi-Apourvari
- grid.412503.10000 0000 9826 9569Department of Petroleum Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
| | - Ahmad Irannejad
- grid.412503.10000 0000 9826 9569Department of Materials Engineering and Metallurgy, Shahid Bahonar University of Kerman, Kerman, Iran
| | - Abdolhossein Hemmati-Sarapardeh
- grid.412503.10000 0000 9826 9569Department of Petroleum Engineering, Shahid Bahonar University of Kerman, Kerman, Iran ,grid.444918.40000 0004 1794 7022Institute of Research and Development, Duy Tan University, Da Nang, 550000 Vietnam ,grid.444918.40000 0004 1794 7022Faculty of Environment and Chemical Engineering, Duy Tan University, Da Nang, 550000 Vietnam
| | - Mahin Schaffie
- grid.412503.10000 0000 9826 9569Department of Petroleum Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
| | - Amir Mosavi
- grid.440535.30000 0001 1092 7422John Von Neumann Faculty of Informatics, Obuda University, Budapest, 1034 Hungary
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Artificial Intelligence Based Methods for Asphaltenes Adsorption by Nanocomposites: Application of Group Method of Data Handling, Least Squares Support Vector Machine, and Artificial Neural Networks. NANOMATERIALS 2020; 10:nano10050890. [PMID: 32384755 PMCID: PMC7279394 DOI: 10.3390/nano10050890] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Revised: 04/22/2020] [Accepted: 04/23/2020] [Indexed: 11/29/2022]
Abstract
Asphaltenes deposition is considered a serious production problem. The literature does not include enough comprehensive studies on adsorption phenomenon involved in asphaltenes deposition utilizing inhibitors. In addition, effective protocols on handling asphaltenes deposition are still lacking. In this study, three efficient artificial intelligent models including group method of data handling (GMDH), least squares support vector machine (LSSVM), and artificial neural network (ANN) are proposed for estimating asphaltenes adsorption onto NiO/SAPO-5, NiO/ZSM-5, and NiO/AlPO-5 nanocomposites based on a databank of 252 points. Variables influencing asphaltenes adsorption include pH, temperature, amount of nanocomposites over asphaltenes initial concentration (D/C0), and nanocomposites characteristics such as BET surface area and volume of micropores. The models are also optimized using nine optimization techniques, namely coupled simulated annealing (CSA), genetic algorithm (GA), Bayesian regularization (BR), scaled conjugate gradient (SCG), ant colony optimization (ACO), Levenberg–Marquardt (LM), imperialistic competitive algorithm (ICA), conjugate gradient with Fletcher-Reeves updates (CGF), and particle swarm optimization (PSO). According to the statistical analysis, the proposed RBF-ACO and LSSVM-CSA are the most accurate approaches that can predict asphaltenes adsorption with average absolute percent relative errors of 0.892% and 0.94%, respectively. The sensitivity analysis shows that temperature has the most impact on asphaltenes adsorption from model oil solutions.
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Montes D, Henao J, Taborda EA, Gallego J, Cortés FB, Franco CA. Effect of Textural Properties and Surface Chemical Nature of Silica Nanoparticles from Different Silicon Sources on the Viscosity Reduction of Heavy Crude Oil. ACS OMEGA 2020; 5:5085-5097. [PMID: 32201795 PMCID: PMC7081395 DOI: 10.1021/acsomega.9b04041] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 02/20/2020] [Indexed: 06/10/2023]
Abstract
The main objective of this study is to evaluate the effect of the textural properties and surface chemical nature of silica nanoparticles obtained from different synthesis routes and silicon precursors, on their interactions with asphaltenes and further viscosity reduction of heavy crude oil (HO). Four different SiO2 nanoparticles were used, namely, commercial fumed silica nanoparticles (CSNs) and three in-house-synthesized nanoparticles (named based on the silicon source) modifying the silicon precursor: sodium silicate (SNSS), tetraethylorthosilicate (TEOS) (SNT), and rice husk (SNRH). The nanomaterials were characterized through dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, N2 physisorption (S BET), atomic force microscopy (AFM), and X-ray photoelectron (XP) spectroscopy (XPS). The adsorption of asphaltenes over the different nanoparticles was evaluated at a concentration of 1000 mg·L-1 in toluene. The asphaltene-nanoparticle interactions are closely related to several textural properties, such as roughness, surface area, and hydrodynamic diameter, as well as the surface chemical nature of the materials. The results in the textural characterization exhibited that the sizes of the nanoparticles from TEM ranged between 6.9 and 11.5 nm. Nevertheless, the standard deviation of the measurements showed that the sizes are statistically similar. Inversely, the hydrodynamic diameter changed, affecting the surface silanol group's availability due to a hindering effect on functional groups as the hydrodynamic size of the material increased. The rheological measurements were performed at a fixed nanoparticle dosage of 1000 mg·L-1 and showed that the trend of the degree of viscosity reduction (DVR) was CSN > SNT > SNSS > SNRH with the highest value yielding at 30%. The results of DVR are in accordance with the nanoparticles' adsorptive capacity as higher values were obtained with the material that leads to a higher amount of adsorbed asphaltenes. Also, the oxygen amount related to silanol groups, estimated by the XPS analysis, showed a direct relation regarding adsorption capacity and further HO viscosity reduction.
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Affiliation(s)
- Daniel Montes
- Grupo
de Investigación en Fenómenos de Superficie Michael
Polanyi, Departamento de Procesos y Energía, Facultad de Minas, Universidad Nacional de Colombia, Sede Medellín, Medellín 050034, Colombia
| | - Jonathan Henao
- Grupo
de Investigación en Fenómenos de Superficie Michael
Polanyi, Departamento de Procesos y Energía, Facultad de Minas, Universidad Nacional de Colombia, Sede Medellín, Medellín 050034, Colombia
| | - Esteban A. Taborda
- Grupo
de Investigación en Fenómenos de Superficie Michael
Polanyi, Departamento de Procesos y Energía, Facultad de Minas, Universidad Nacional de Colombia, Sede Medellín, Medellín 050034, Colombia
| | - Jaime Gallego
- Grupo
de Investigación en Fenómenos de Superficie Michael
Polanyi, Departamento de Procesos y Energía, Facultad de Minas, Universidad Nacional de Colombia, Sede Medellín, Medellín 050034, Colombia
- Química
de Recursos Energéticos y Medio Ambiente, Instituto de Química, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín 050010, Colombia
| | - Farid B. Cortés
- Grupo
de Investigación en Fenómenos de Superficie Michael
Polanyi, Departamento de Procesos y Energía, Facultad de Minas, Universidad Nacional de Colombia, Sede Medellín, Medellín 050034, Colombia
| | - Camilo A. Franco
- Grupo
de Investigación en Fenómenos de Superficie Michael
Polanyi, Departamento de Procesos y Energía, Facultad de Minas, Universidad Nacional de Colombia, Sede Medellín, Medellín 050034, Colombia
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8
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Shi C, Xie L, Zhang L, Lu X, Zeng H. Probing the interaction mechanism between oil droplets with asphaltenes and solid surfaces using AFM. J Colloid Interface Sci 2020; 558:173-181. [DOI: 10.1016/j.jcis.2019.09.092] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 09/23/2019] [Accepted: 09/24/2019] [Indexed: 11/25/2022]
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9
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Zhang J, Zhang L, Cui X, Gong L, Xiang L, Shi C, Hu W, Zeng H. Scalable polyzwitterion-polydopamine coating for regenerable oil/water separation and underwater self-cleaning of stubborn heavy oil fouling without pre-hydration. Chem Commun (Camb) 2018; 54:9734-9737. [PMID: 30074029 DOI: 10.1039/c8cc04611e] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A facile and scalable polyzwitterion-polydopamine coating strategy has been developed to functionalize substrates and sponges. This approach, for the first time, achieves superior regenerable underwater self-cleaning of stubborn asphaltenes-containing heavy oil fouling without pre-hydration and removal of water residues from heavy oil, with significant implications in many engineering and environmental processes.
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Affiliation(s)
- Jiawen Zhang
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
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10
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Hernández-Bravo R, Miranda AD, Martínez-Magadán JM, Domínguez JM. Experimental and Theoretical Study on Supramolecular Ionic Liquid (IL)-Asphaltene Complex Interactions and Their Effects on the Flow Properties of Heavy Crude Oils. J Phys Chem B 2018; 122:4325-4335. [PMID: 29587484 DOI: 10.1021/acs.jpcb.8b01061] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A combined study for understanding the molecular interactions of asphaltenes with molecular species such as ionic liquids (ILs) comprised experimental measurements and computational numerical simulation calculations, using density-functional theory (DFT) with dispersion corrections, molecular dynamics (MD) calculations, and experimental rheological characterization of the heavy crude oils (HCOs), before and after doping with ILs, respectively. The main results show that ILs influence the asphaltenic dimer association by forming supramolecular complexes that modify the properties of crude oils such as viscosity and interfacial tension. The IL-cation and asphaltene-π ligand molecular interactions seem to dominate the interactions between ionic liquids and asphaltenes, where ILs' high aromaticity index induces a strong interaction with the aromatic hard core of asphaltenes.
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Affiliation(s)
- R Hernández-Bravo
- Instituto Mexicano del Petróleo , Eje Central Lázaro Cárdenas Norte 152, Col. San Bartolo Atepehuacan, Gustavo A. Madero , México City , C.P. 07730 , México
| | - A D Miranda
- Instituto Mexicano del Petróleo , Eje Central Lázaro Cárdenas Norte 152, Col. San Bartolo Atepehuacan, Gustavo A. Madero , México City , C.P. 07730 , México
| | - J-M Martínez-Magadán
- Instituto Mexicano del Petróleo , Eje Central Lázaro Cárdenas Norte 152, Col. San Bartolo Atepehuacan, Gustavo A. Madero , México City , C.P. 07730 , México
| | - J M Domínguez
- Instituto Mexicano del Petróleo , Eje Central Lázaro Cárdenas Norte 152, Col. San Bartolo Atepehuacan, Gustavo A. Madero , México City , C.P. 07730 , México
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Pradilla D, Subramanian S, Simon S, Sjöblom J, Beurroies I, Denoyel R. Microcalorimetry Study of the Adsorption of Asphaltenes and Asphaltene Model Compounds at the Liquid-Solid Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:7294-7305. [PMID: 27348137 DOI: 10.1021/acs.langmuir.6b00816] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The adsorption of an acidic polyaromatic asphaltene model compound (C5PeC11) and indigenous C6-asphaltenes onto the liquid-solid surface is studied. Model compound C5PeC11 exhibits a similar type of adsorption with a plateau adsorbed amount as C6-asphaltenes onto three surfaces (silica, calcite, and stainless steel). Model compound BisAC11, with aliphatic end groups and no acidic functionality, does not adsorb at the liquid-silica surface, indicating the importance of polar interactions on adsorption. The values of the adsorption enthalpy characterized by the ΔHz parameter (the enthalpy at zero coverage) indicate that the type of adsorption and the driving force depend on the surface, a key feature when discussing asphaltene deposition. The adsorption of C5PeC11 onto silica is shown to be driven primarily by H bonding (ΔHz = -34.9 kJ/mol), unlike adsorption onto calcite where polar van der Waals and acidic/basic interactions are thought to be predominant (ΔHz = -23.5 kJ/mol). Interactions between C5PeC11 and stainless steel are found to be weak (ΔHz = -7.7 kJ/mol). Comparing C6-asphaltenes and their esterified counterpart shows that adsorption at the liquid-solid surface is not influenced by the formation of H bonds. This was evidenced by the similar adsorbed amounts obtained. Finally, C5PeC11 captures, to a certain extent, the adsorption interactions of asphaltenes present at the calcite-oil and stainless steel-oil surfaces.
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Affiliation(s)
- Diego Pradilla
- Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU) , NO-7491 Trondheim, Norway
| | - Sreedhar Subramanian
- Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU) , NO-7491 Trondheim, Norway
| | - Sébastien Simon
- Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU) , NO-7491 Trondheim, Norway
| | - Johan Sjöblom
- Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU) , NO-7491 Trondheim, Norway
| | - Isabelle Beurroies
- Aix Marseille Université, CNRS, MADIREL UMR 7246, 13397 Marseille cedex 20, France
| | - Renaud Denoyel
- Aix Marseille Université, CNRS, MADIREL UMR 7246, 13397 Marseille cedex 20, France
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12
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Development of a support for a NiO catalyst for selective adsorption and post-adsorption catalytic steam gasification of thermally converted asphaltenes. Catal Today 2013. [DOI: 10.1016/j.cattod.2012.05.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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13
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Mansueto M, Sauer S, Butschies M, Kaller M, Baro A, Woerner R, Hansen NH, Tovar G, Pflaum J, Laschat S. Triphenylene silanes for direct surface anchoring in binary mixed self-assembled monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:8399-8407. [PMID: 22616616 DOI: 10.1021/la300775n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
New triphenylene-based silanes 2-(ω-(chlorodimethylsilyl)-n-alkyl)-3,6,7,10,11-penta-m-alkoxytriphenylene 4 (Tm-Cn) with n = 8 or 9 and m = 7, 8, 9, 10, or 11 were synthesized, and their self-assembly behavior in the liquid state and at glass and silicon oxide surfaces was investigated. The mesomorphic properties of triphenylene silanes 4 (Tm-Cn) and their precursors 3 (Tm-Cn) were determined by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction. From the small-angle X-ray scattering (SAXS) regime, a preferential discotic lamellar mesophase can be deduced, and wide-angle X-ray scattering (WAXS) highlights the liquid-like characteristics of the alkyl side chains. To transfer these bulk structural properties to thin films, self-assembled monolayers (SAMs) were obtained by adsorption from solution and characterized by water contact angle measurements, null ellipsometry, and atomic force microscopy (AFM). Employing the concentration as an additional degree of freedom, binary SAMs of 2-(ω-(chlorodimethylsilyl)-undecyl)-3,6,7,10,11-penta-decyloxytriphenylene 4 (T10-C11) were coassembled with chlorodecyldimethylsilane or chlorodimethyloctadecylsilane, and their capability as model systems for organic templating was evaluated. The structure of the resulting binary mixed SAMs was analyzed by water contact angle measurements, null ellipsometry, and X-ray reflectivity (XRR) in combination with theoretical modeling by a multidimensional Parratt algorithm and AFM. The composition dependence of film thickness and roughness can be explained by a microscopic model including the steric hindrance of the respective molecular constituents.
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Affiliation(s)
- Markus Mansueto
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
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14
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Desbief S, Patrone L, Goguenheim D, Vuillaume D. Different types of phase separation in binary monolayers of long chain alkyltrichlorosilanes on silicon oxide. RSC Adv 2012. [DOI: 10.1039/c2ra01327d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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15
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Patrone L, Gadenne V, Desbief S. Single and binary self-assembled monolayers of phenyl- and pentafluorophenyl-based silane species, and their phase separation with octadecyltrichlorosilane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:17111-17118. [PMID: 20968285 DOI: 10.1021/la102742e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this paper, we first present the study of the formation of phenyltrichlorosilane film and self-assembled monolayers of phenylalkyltrichlorosilane (PATCl), pentafluoro-phenylalkyltrichlorosilane (PFATCl), and a mixture of the two, on silicon covered by its native oxide. These monolayers are shown to grow in two steps with characteristic time constants. The first step is characterized by a similar time constant of growth for all the studied trichlorosilane molecules and attributed to chemisorption. The second step corresponds to the arrangement between molecules, accelerated by the presence of the short alkyl chain (3-4 carbon atoms), and by mixing phenyl and pentafluoro-phenyl terminal moieties, which is accounted for by hydrogen bonding CH···FC and/or attractive quadrupolar interactions within a face-to-face phenyl/pentafluoro-phenyl alternating stack arrangement. Such results should allow improvement of intermolecular stacking within conjugated molecular domains, which is particularly important for molecular electronic devices. In the second part, we studied how PATCl, PFATCl, and their mixture phase separate with octadecyltrichlorosilane (OTS) molecules in various ratios. The way to improve phase separation was studied modifying aromatic ring to ring as well as aromatic-aliphatic interactions. OTS island size and coverage are shown to be smaller with the aromatic phase that involves stronger ring to ring interactions, i.e., attractive interactions between the phenyl species by mixing phenyl and pentafluoro-phenyl rings. The best phase separation is obtained with PFATCl as the aromatic molecule. If nanoislands of aromatic molecules could not be observed in these experiments, we show that they are attainable by mixing OTS and aromatic small organotriethoxysilanes whose grafting kinetics is slower. These results pave the way to the control improvement of the composition and nanostructuration of SAMs, essential for their further use within molecular devices.
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Affiliation(s)
- Lionel Patrone
- Aix-Marseille Université, IM2NP, Maison des Technologies, Place Georges Pompidou, F-83000 Toulon, France.
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