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Copy file name to clipboardexpand all lines: testimonials.bib
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publisher={Cold Spring Harbor Laboratory}
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@article{Gresham2024,
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author = {Gresham, Isaac J and Johnson, Edwin C and Robertson, Hayden and Willott, Joshua D and Webber, Grant B and Wanless, Erica J and Nelson, Andrew R J and Prescott, Stuart W},
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doi = {10.1016/j.jcis.2023.10.101},
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issn = {0021-9797},
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journal = {Journal of Colloid And Interface Science},
abstract = {Hypersaline environments are ubiquitous in nature and are found in myriad technological processes. Recent empirical studies have revealed a significant discrepancy between predicted and observed screening lengths at high salt concentrations{,} a phenomenon referred to as underscreening. Herein we investigate underscreening using a cationic polyelectrolyte brush as an exemplar. Poly(2-(methacryloyloxy)ethyl)trimethylammonium (PMETAC) brushes were synthesised and their internal structural changes and swelling response was monitored with neutron reflectometry and spectroscopic ellipsometry. Both techniques revealed a monotonic brush collapse as the concentration of symmetric monovalent electrolyte increased. However{,} a non-monotonic change in brush thickness was observed in all multivalent electrolytes at higher concentrations{,} known as re-entrant swelling; indicative of underscreening. For all electrolytes{,} numerical self-consistent field theory predictions align with experimental studies in the low-to-moderate salt concentration regions. Analysis suggests that the classical theory of electrolytes is insufficient to describe the screening lengths observed at high salt concentrations and that the re-entrant polyelectrolyte brush swelling seen herein is consistent with the so-called regular underscreening phenomenon.},
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author = {Robertson, Hayden and Elliott, Gareth R and Nelson, Andrew R J and {Le Brun}, Anton P and Webber, Grant B and Prescott, Stuart W and Craig, Vincent S J and Wanless, Erica J and Willott, Joshua D},
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doi = {10.1039/D3CP02206D},
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journal = {Physical Chemistry Chemical Physics},
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number = {36},
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pages = {24770--24782},
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publisher = {The Royal Society of Chemistry},
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title = {{Underscreening in concentrated electrolytes: re-entrant swelling in polyelectrolyte brushes}},
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url = {http://dx.doi.org/10.1039/D3CP02206D},
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volume = {25},
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year = {2023}
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}
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@article{Robertson2024,
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abstract = {Pertinent to cryopreservation as well as energy storage and batteries, nonaqueous electrolytes and their mixtures with water were investigated. In particular, specific ion-induced effects on the modulation of a poly(N-isopropylacrylamide) (PNIPAM) brush were investigated in various dimethyl sulfoxide (DMSO)–water solvent mixtures. Spectroscopic ellipsometry and neutron reflectometry were employed to probe changes in brush swelling and structure, respectively. In water-rich solvents (i.e., pure water and 6 mol % DMSO), PNIPAM undergoes a swollen to collapsed thermotransition with increasing temperature, whereby a forward Hofmeister series was noted; K+ and Li+ electrolytes composed of SCN– and I– salted-in (stabilized) PNIPAM chains, and electrolytes of Cl– and Br– salted-out (destabilized) the polymer. The cation was seen to play a lesser role than that of the anion, merely modulating the magnitude of the anion effect. In 70 mol % DMSO, a collapsed to swollen thermotransition was noted for PNIPAM. Here, concentration-dependent specific ion effects were observed; a forward series was observed in 0.2 mol % electrolytes, whereas increasing the electrolyte concentration to 0.9 mol % led to a series reversal. While no thermotransition was observed in pure DMSO, a solvent-induced specific ion series reversal was noted; SCN– destabilized the brush and Cl– stabilized the brush. Both series reversals are attributed to the delicate balance of interactions between the solvent, solute (ion), and substrate (brush). Namely, the stability of the solvent clusters was hypothesized to drive polymer solvation.},
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author = {Robertson, Hayden and Gresham, Isaac J and Nelson, Andrew R J and Gregory, Kasimir P and Johnson, Edwin C and Willott, Joshua D and Prescott, Stuart W and Webber, Grant B and Wanless, Erica J},
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doi = {10.1021/acs.langmuir.3c02596},
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issn = {0743-7463},
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journal = {Langmuir},
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month = {jan},
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number = {1},
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pages = {335--347},
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publisher = {American Chemical Society},
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title = {{Solvent-Modulated Specific Ion Effects: Poly(N-isopropylacrylamide) Brushes in Nonaqueous Electrolytes}},
abstract = {Cosolvents play an integral role in polymer solubility, with myriad applications in drug delivery and energy storage. In particular, dimethyl sulfoxide (DMSO) has received substantial attention to date due to its cryoprotective properties and interesting nonideal mixing behaviour. Here, for the first time, we probe the fundamentals of DMSO–water solvent structuring using a thermoresponsive poly(N-isopropoylacrylamide) (PNIPAM) brush as an exemplar. Spectroscopic ellipsometry and neutron reflectometry were employed to monitor changes in brush swelling and conformation as a function of temperature and solvent composition, whereby changes in solvent structure can be deduced. Importantly, unlike free polymer, grafted polymers permit measurements across the entire solvent composition space, including ‘poor' solvent conditions, permitting the characterisation of polymers in complex media for future technologies. In the water-rich regime, the prevalent hydrogen-bond network resulted in the PNIPAM brush exhibiting a lower critical solution temperature (LCST) up to DMSO mole fractions of 0.10 (xD = 0.10), which decreased with increasing xD; DMSO is a chaotropic cosolvent. This region was adjacent to a cononsolvency region. Interestingly, reentrant swelling was observed for above approximately xD = 0.2. In DMSO-rich regimes, non-site-specific dipole–dipole interactions resulted in the PNIPAM brush exhibiting an uppercritical solution temperature (UCST), whereby the periphery of the swollen brush was more diffuse than at low xD. At all temperatures, pure DMSO is a good solvent for PNIPAM and no thermoresponse was observed. Herein we demonstrate how the structure and swelling of a polymer brush film can be modulated by tuning solvent composition by mixing two ‘good' solvents.},
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author = {Robertson, Hayden and Nelson, Andrew R J and Prescott, Stuart W and Webber, Grant B and Wanless, Erica J},
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doi = {10.1039/D2PY01487D},
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issn = {1759-9954},
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journal = {Polymer Chemistry},
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number = {13},
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pages = {1526--1535},
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publisher = {The Royal Society of Chemistry},
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title = {{Cosolvent effects on the structure and thermoresponse of a polymer brush: PNIPAM in DMSO–water mixtures}},
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url = {http://dx.doi.org/10.1039/D2PY01487D},
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volume = {14},
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year = {2023}
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}
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@article{ROBERTSON2024103238,
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title = {Illuminating the nanostructure of diffuse interfaces: Recent advances and future directions in reflectometry techniques},
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journal = {Advances in Colloid and Interface Science},
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pages = {103238},
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year = {2024},
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issn = {0001-8686},
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doi = {https://doi.org/10.1016/j.cis.2024.103238},
abstract = {Diffuse soft matter interfaces take many forms, from end-tethered polymer brushes or adsorbed surfactants to self-assembled layers of lipids. These interfaces play crucial roles across a multitude of fields, including materials science, biophysics, and nanotechnology. Understanding the nanostructure and properties of these interfaces is fundamental for optimising their performance and designing novel functional materials. In recent years, reflectometry techniques, in particular neutron reflectometry, have emerged as powerful tools for elucidating the intricate nanostructure of soft matter interfaces with remarkable precision and depth. This review provides an overview of selected recent developments in reflectometry and their applications for illuminating the nanostructure of diffuse interfaces. We explore various principles and methods of neutron and X-ray reflectometry, as well as ellipsometry, and discuss advances in their experimental setups and data analysis approaches. Improvements to experimental neutron reflectometry methods have enabled greater time resolution in kinetic measurements and elucidation of diffuse structure under shear or confinement, while innovation in analysis protocols has significantly reduced data processing times, facilitated co-refinement of reflectometry data from multiple instruments and provided greater-than-ever confidence in proposed structural models. Furthermore, we highlight some significant research findings enabled by these techniques, revealing the organisation, dynamics, and interfacial phenomena at the nanoscale. We also discuss future directions and potential advancements in reflectometry techniques. By shedding light on the nanostructure of diffuse interfaces, reflectometry techniques enable the rational design and tailoring of interfaces with enhanced properties and functionalities.}
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