Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in n-dodecane with varying water content onto iron oxide

Alexander J. Armstrong; Rui F.G. Apóstolo; Thomas M. McCoy; Finian J. Allen; James Doutch; Beatrice N. Cattoz; Peter J. Dowding; Rebecca J.L. Welbourn; Alexander F. Routh; Philip J. Camp

doi:10.1039/d3nr05080g

Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in n-dodecane with varying water content onto iron oxide

Alexander J. Armstrong, Rui F.G. Apóstolo, Thomas M. McCoy, Finian J. Allen, James Doutch, Beatrice N. Cattoz, Peter J. Dowding, Rebecca J.L. Welbourn, Alexander F. Routh, Philip J. Camp

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Abstract

The self-assembly and surface adsorption of glycerol monooleate (GMO) in n-dodecane are studied using a combination of experimental and molecular dynamics simulation techniques. The self-assembly of GMO to form reverse micelles, with and without added water, is studied using small-angle neutron scattering and simulations. A large-scale simulation is also used to investigate the self-assembly kinetics. GMO adsorption onto iron oxide is studied using depletion isotherms, neutron reflectometry, and simulations. The adsorbed amounts of GMO, and any added water, are determined experimentally, and the structures of the adsorbed films are investigated using reflectometry. Detailed fitting and analysis of the reflectometry measurements are presented, taking into account various factors such as surface roughness, and the presence of impurities. The reflectometry measurements are complemented by molecular dynamics simulations, and good consistency between both approaches is demonstrated by direct comparison of measured and simulated reflectivity and scattering length density profiles. The results of this analysis are that in dry systems, GMO adsorbs as self-assembled reverse micelles with some molecules adsorbing directly to the surface through the polar head groups, while in wet systems, the GMO is adsorbed onto a thin layer of water. Only at high surface coverage is some water trapped inside a reverse-micelle structure; at lower surface coverages, the GMO molecules associate primarily with the water layer, rather than self-assemble.

Original language	English
Pages (from-to)	1952-1970
Number of pages	19
Journal	Nanoscale
Volume	16
Issue number	4
DOIs	https://doi.org/10.1039/d3nr05080g
State	Published - Dec 21 2023
Externally published	Yes

Funding

This work was supported by Infineum UK Ltd through a PhD studentship to AJA, and research fellowships to AJA, RFGA, and TMMcC. TMMcC acknowledges the support of the Ernest Oppenheimer Fund through provision of an Oppenheimer Research Fellowship at the University of Cambridge. The neutron reflectometry data were analysed using the computing resources provided by STFC Scientific Computing Department's SCARF cluster. The authors gratefully acknowledge STFC for the peer-review access to the INTER neutron reflectometer at ISIS (https://doi.org/10.5286/ISIS.E.RB1920367). The authors thank Zlatko Saracevic for conducting the N2 BET sorption analysis. This work used the ARCHER2 UK National Supercomputing Service (https://www.archer2.ac.uk). RFGA and PJC thank Dr Julien Sindt for help with benchmarking, testing, and monitoring the 2-million-atom simulation on ARCHER2, and the Nvidia Corporation for the donation of Titan Xp and Titan V GPUs used in the research. The authors are grateful to the anonymous referees for their constructive comments. This work was supported by Infineum UK Ltd through a PhD studentship to AJA, and research fellowships to AJA, RFGA, and TMMcC. TMMcC acknowledges the support of the Ernest Oppenheimer Fund through provision of an Oppenheimer Research Fellowship at the University of Cambridge. The neutron reflectometry data were analysed using the computing resources provided by STFC Scientific Computing Department's SCARF cluster. The authors gratefully acknowledge STFC for the peer-review access to the INTER neutron reflectometer at ISIS ( https://doi.org/10.5286/ISIS.E.RB1920367 ). The authors thank Zlatko Saracevic for conducting the N BET sorption analysis. This work used the ARCHER2 UK National Supercomputing Service ( https://www.archer2.ac.uk ). RFGA and PJC thank Dr Julien Sindt for help with benchmarking, testing, and monitoring the 2-million-atom simulation on ARCHER2, and the Nvidia Corporation for the donation of Titan Xp and Titan V GPUs used in the research. The authors are grateful to the anonymous referees for their constructive comments. 2

Funders	Funder number
Ernest Oppenheimer Fund
ISIS
Infineum UK Ltd
TMMcC
Science and Technology Facilities Council
University of Cambridge

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10.1039/d3nr05080g

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Armstrong, A. J., Apóstolo, R. F. G., McCoy, T. M., Allen, F. J., Doutch, J., Cattoz, B. N., Dowding, P. J., Welbourn, R. J. L., Routh, A. F., & Camp, P. J. (2023). Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in n-dodecane with varying water content onto iron oxide. Nanoscale, 16(4), 1952-1970. https://doi.org/10.1039/d3nr05080g

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title = "Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in n-dodecane with varying water content onto iron oxide",

abstract = "The self-assembly and surface adsorption of glycerol monooleate (GMO) in n-dodecane are studied using a combination of experimental and molecular dynamics simulation techniques. The self-assembly of GMO to form reverse micelles, with and without added water, is studied using small-angle neutron scattering and simulations. A large-scale simulation is also used to investigate the self-assembly kinetics. GMO adsorption onto iron oxide is studied using depletion isotherms, neutron reflectometry, and simulations. The adsorbed amounts of GMO, and any added water, are determined experimentally, and the structures of the adsorbed films are investigated using reflectometry. Detailed fitting and analysis of the reflectometry measurements are presented, taking into account various factors such as surface roughness, and the presence of impurities. The reflectometry measurements are complemented by molecular dynamics simulations, and good consistency between both approaches is demonstrated by direct comparison of measured and simulated reflectivity and scattering length density profiles. The results of this analysis are that in dry systems, GMO adsorbs as self-assembled reverse micelles with some molecules adsorbing directly to the surface through the polar head groups, while in wet systems, the GMO is adsorbed onto a thin layer of water. Only at high surface coverage is some water trapped inside a reverse-micelle structure; at lower surface coverages, the GMO molecules associate primarily with the water layer, rather than self-assemble.",

author = "Armstrong, {Alexander J.} and Ap{\'o}stolo, {Rui F.G.} and McCoy, {Thomas M.} and Allen, {Finian J.} and James Doutch and Cattoz, {Beatrice N.} and Dowding, {Peter J.} and Welbourn, {Rebecca J.L.} and Routh, {Alexander F.} and Camp, {Philip J.}",

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doi = "10.1039/d3nr05080g",

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T1 - Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in n-dodecane with varying water content onto iron oxide

AU - Armstrong, Alexander J.

AU - Apóstolo, Rui F.G.

AU - McCoy, Thomas M.

AU - Allen, Finian J.

AU - Doutch, James

AU - Cattoz, Beatrice N.

AU - Dowding, Peter J.

AU - Welbourn, Rebecca J.L.

AU - Routh, Alexander F.

AU - Camp, Philip J.

PY - 2023/12/21

Y1 - 2023/12/21

N2 - The self-assembly and surface adsorption of glycerol monooleate (GMO) in n-dodecane are studied using a combination of experimental and molecular dynamics simulation techniques. The self-assembly of GMO to form reverse micelles, with and without added water, is studied using small-angle neutron scattering and simulations. A large-scale simulation is also used to investigate the self-assembly kinetics. GMO adsorption onto iron oxide is studied using depletion isotherms, neutron reflectometry, and simulations. The adsorbed amounts of GMO, and any added water, are determined experimentally, and the structures of the adsorbed films are investigated using reflectometry. Detailed fitting and analysis of the reflectometry measurements are presented, taking into account various factors such as surface roughness, and the presence of impurities. The reflectometry measurements are complemented by molecular dynamics simulations, and good consistency between both approaches is demonstrated by direct comparison of measured and simulated reflectivity and scattering length density profiles. The results of this analysis are that in dry systems, GMO adsorbs as self-assembled reverse micelles with some molecules adsorbing directly to the surface through the polar head groups, while in wet systems, the GMO is adsorbed onto a thin layer of water. Only at high surface coverage is some water trapped inside a reverse-micelle structure; at lower surface coverages, the GMO molecules associate primarily with the water layer, rather than self-assemble.

AB - The self-assembly and surface adsorption of glycerol monooleate (GMO) in n-dodecane are studied using a combination of experimental and molecular dynamics simulation techniques. The self-assembly of GMO to form reverse micelles, with and without added water, is studied using small-angle neutron scattering and simulations. A large-scale simulation is also used to investigate the self-assembly kinetics. GMO adsorption onto iron oxide is studied using depletion isotherms, neutron reflectometry, and simulations. The adsorbed amounts of GMO, and any added water, are determined experimentally, and the structures of the adsorbed films are investigated using reflectometry. Detailed fitting and analysis of the reflectometry measurements are presented, taking into account various factors such as surface roughness, and the presence of impurities. The reflectometry measurements are complemented by molecular dynamics simulations, and good consistency between both approaches is demonstrated by direct comparison of measured and simulated reflectivity and scattering length density profiles. The results of this analysis are that in dry systems, GMO adsorbs as self-assembled reverse micelles with some molecules adsorbing directly to the surface through the polar head groups, while in wet systems, the GMO is adsorbed onto a thin layer of water. Only at high surface coverage is some water trapped inside a reverse-micelle structure; at lower surface coverages, the GMO molecules associate primarily with the water layer, rather than self-assemble.

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Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in n-dodecane with varying water content onto iron oxide

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