2025
Edwin C. Johnson; Hayden Robertson; Erica J. Wanless; Grant B. Webber; Ben A. Humphreys
Neutron reflectometry can capture the rapid collapse and swelling of a polymer brush Journal Article
In: Journal of Colloid and Interface Science, vol. 699, pp. 138248, 2025, ISSN: 0021-9797.
@article{Johnson_2025i,
title = {Neutron reflectometry can capture the rapid collapse and swelling of a polymer brush},
author = {Edwin C. Johnson and Hayden Robertson and Erica J. Wanless and Grant B. Webber and Ben A. Humphreys},
url = {http://dx.doi.org/10.1016/j.jcis.2025.138248},
doi = {10.1016/j.jcis.2025.138248},
issn = {0021-9797},
year = {2025},
date = {2025-12-01},
journal = {Journal of Colloid and Interface Science},
volume = {699},
pages = {138248},
publisher = {Elsevier BV},
abstract = {Hypothesis: Measuring dynamic processes in responsive soft matter systems remains a critical frontier in bridging fundamental studies and applied sciences. In particular, determining structural changes of surface-grafted polymers due to the application of stimuli remains poorly examined due to historical instrument limitations. Herein, we exploit the high flux capabilities of the D17 neutron reflectometer (Institut Laue-Langevin, France) to examine kinetic changes in the internal nanostructure of a poly(N-isopropyl-acrylamide) (PNIPAM) brush with temperature or the presence of a common osmolyte (glucose). Experiments: Ellipsometry and neutron reflectometry (NR) was employed to examine changes in brush thickness as a function of temperature in water and aqueous glucose solutions under equilibrium conditions. NR captured the kinetics of brush swelling/collapse triggered by rapid temperature or glucose concentration changes. Findings: Ellipsometry and NR revealed a decrease in the lower critical solution temperature (LCST) of a PNIPAM brush with increasing glucose concentration. Equilibrium NR measurements showed vertical phase separation within the brush when in a near-collapsed state. This stratified structure was expected for the thermally triggered conformation changes, but has not been observed for glucose-triggered collapse/swelling. Excellent statistics were achieved over intervals for the NR kinetic measurements with modelled profiles comparable to longer equilibrium measurements across a wider q range. A small hysteresis was observed in the temperature induced swelling/collapse, while a more pronounced hysteresis was observed in the glucose triggered conformational changes. This hysteresis was equivalent for both swelling and collapse transitions and is attributed to preferential adsorption of the glucose in the brush. Copyright},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hypothesis: Measuring dynamic processes in responsive soft matter systems remains a critical frontier in bridging fundamental studies and applied sciences. In particular, determining structural changes of surface-grafted polymers due to the application of stimuli remains poorly examined due to historical instrument limitations. Herein, we exploit the high flux capabilities of the D17 neutron reflectometer (Institut Laue-Langevin, France) to examine kinetic changes in the internal nanostructure of a poly(N-isopropyl-acrylamide) (PNIPAM) brush with temperature or the presence of a common osmolyte (glucose). Experiments: Ellipsometry and neutron reflectometry (NR) was employed to examine changes in brush thickness as a function of temperature in water and aqueous glucose solutions under equilibrium conditions. NR captured the kinetics of brush swelling/collapse triggered by rapid temperature or glucose concentration changes. Findings: Ellipsometry and NR revealed a decrease in the lower critical solution temperature (LCST) of a PNIPAM brush with increasing glucose concentration. Equilibrium NR measurements showed vertical phase separation within the brush when in a near-collapsed state. This stratified structure was expected for the thermally triggered conformation changes, but has not been observed for glucose-triggered collapse/swelling. Excellent statistics were achieved over intervals for the NR kinetic measurements with modelled profiles comparable to longer equilibrium measurements across a wider q range. A small hysteresis was observed in the temperature induced swelling/collapse, while a more pronounced hysteresis was observed in the glucose triggered conformational changes. This hysteresis was equivalent for both swelling and collapse transitions and is attributed to preferential adsorption of the glucose in the brush. Copyright
Hayden Robertson; Joshua D. Willott; Andrew R. J. Nelson; Stuart W. Prescott; Erica J. Wanless; B. Grant Webber
Solvent and Ion-Mediated Behavior of a Thermoresponsive Brush: Specific Ion Effects in Methanol-Water Electrolytes Journal Article
In: Macromolecular Rapid Communications, 2025, ISSN: 1521-3927.
@article{Robertson_2025,
title = {Solvent and Ion-Mediated Behavior of a Thermoresponsive Brush: Specific Ion Effects in Methanol-Water Electrolytes},
author = {Hayden Robertson and Joshua D. Willott and Andrew R. J. Nelson and Stuart W. Prescott and Erica J. Wanless and B. Grant Webber},
url = {http://dx.doi.org/10.1002/marc.202500093},
doi = {10.1002/marc.202500093},
issn = {1521-3927},
year = {2025},
date = {2025-05-01},
journal = {Macromolecular Rapid Communications},
publisher = {Wiley},
abstract = {In this study, specific ion effects are explored in methanol-water mixtures, which play a critical role in a diverse range of applications, including protein solubilization and supercapacitors. Spectroscopic ellipsometry and neutron reflectometry are employed to investigate the solvent- and ion-mediated behavior of a poly(N-isopropylacrylamide) (PNIPAM) brush, a well-known thermoresponsive polymer. In the absence of ions and at low methanol mole fractions (xM), PNIPAM displays lower critical solution temperature (LCST) type behavior, with the thermotransition temperature decreasing as xM increased. Upon further increasing xM, a cononsolvency region is identified at approximately xM = 0.15, beyond which re-entrant swelling is observed in conjunction with a suppressed thermoresponse. In the presence of xM = 0.10 electrolytes, the observed specific ion effects adhere to a forward Hofmeister series. Strongly solvated ions, such as Cl- and Br-, decrease the LCST of the brush. In contrast, poorly solvated ions, such as SCN- and I-, lead to more swollen brush profiles and an increase in the LCST. We hypothesize that the stability of water-methanol clusters plays a crucial role in governing polymer solvation, providing insights into the fundamental interactions within mixed solvent systems. Moreover, a theoretical ion that does not impact the swelling or structure of a PNIPAM brush is proposed.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this study, specific ion effects are explored in methanol-water mixtures, which play a critical role in a diverse range of applications, including protein solubilization and supercapacitors. Spectroscopic ellipsometry and neutron reflectometry are employed to investigate the solvent- and ion-mediated behavior of a poly(N-isopropylacrylamide) (PNIPAM) brush, a well-known thermoresponsive polymer. In the absence of ions and at low methanol mole fractions (xM), PNIPAM displays lower critical solution temperature (LCST) type behavior, with the thermotransition temperature decreasing as xM increased. Upon further increasing xM, a cononsolvency region is identified at approximately xM = 0.15, beyond which re-entrant swelling is observed in conjunction with a suppressed thermoresponse. In the presence of xM = 0.10 electrolytes, the observed specific ion effects adhere to a forward Hofmeister series. Strongly solvated ions, such as Cl- and Br-, decrease the LCST of the brush. In contrast, poorly solvated ions, such as SCN- and I-, lead to more swollen brush profiles and an increase in the LCST. We hypothesize that the stability of water-methanol clusters plays a crucial role in governing polymer solvation, providing insights into the fundamental interactions within mixed solvent systems. Moreover, a theoretical ion that does not impact the swelling or structure of a PNIPAM brush is proposed.
Edwin C. Johnson; Kasimir P. Gregory; Hayden Robertson; Isaac J. Gresham; Andrew R. J. Nelson; Vincent S. J. Craig; Stuart W. Prescott; Alister J. Page; Grant B. Webber; Erica J. Wanless
The inductive effect does not explain electron density in haloacetates: are our textbooks wrong? Journal Article
In: Chemical Science, 2025, ISSN: 2041-6539.
@article{Johnson_2025,
title = {The inductive effect does not explain electron density in haloacetates: are our textbooks wrong?},
author = {Edwin C. Johnson and Kasimir P. Gregory and Hayden Robertson and Isaac J. Gresham and Andrew R. J. Nelson and Vincent S. J. Craig and Stuart W. Prescott and Alister J. Page and Grant B. Webber and Erica J. Wanless},
url = {http://dx.doi.org/10.1039/D4SC04832F},
doi = {10.1039/d4sc04832f},
issn = {2041-6539},
year = {2025},
date = {2025-01-01},
journal = {Chemical Science},
publisher = {Royal Society of Chemistry (RSC)},
abstract = {Wave functional theory calculations and experiments reveal that the inductive effect does not explain pKa and charge density trends in haloacetates.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Wave functional theory calculations and experiments reveal that the inductive effect does not explain pKa and charge density trends in haloacetates.
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181i,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181ii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
abstract = {The paper addresses the vertical and lateral structure of microgels (MGs) layers at the air/water interface and the effect of Langmuir-Blodgett (LB) transfer on solid substrates on the structure. The MGs are based on poly($N$-isopropylacrylamide) networks. For studying the structure at the air/water interface specular and off-specular X-ray reflectivity (OSR/XRR) allows in situ measurements without any labelling techniques. The initial ex situ atomic force microscopy (AFM) scans of LB-transferred MGs at the air/solid interface reveal strong lateral 2D hexagonal ordering across a broad range of lateral surface pressures at the air/water interface before LB-transfer. Notably, for the first time, these results were confirmed by OSR, demonstrating the existence of the long-range hexagonal ordering at low and intermediate surface pressures. For in situ conditions and upon uniaxial compression at the air/water interface, the MG lattice constant decreases non-monotonically. This indicates the formation of domains at low pressures, that approach each other and only compress when the surface isotherm reaches a plateau. Comparing results of in situ and ex situ measurements, our study clearly shows a transfer effect during the LB-deposition on the lateral ordering of the MGs: The distance between the particles decrease during LB-transfer and at high pressures ($Π,>,22,mathrmmNm^-1$) a second distance occurs indicating small domains with hexagonal internal ordering. The novel surface characterisation approaches here highlight the use of both XRR and OSR to probe the vertical and lateral structure of adsorbed MGs, offering in situ, non-invasive insights without the need for doping or transfer-induced artefacts.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
The paper addresses the vertical and lateral structure of microgels (MGs) layers at the air/water interface and the effect of Langmuir-Blodgett (LB) transfer on solid substrates on the structure. The MGs are based on poly($N$-isopropylacrylamide) networks. For studying the structure at the air/water interface specular and off-specular X-ray reflectivity (OSR/XRR) allows in situ measurements without any labelling techniques. The initial ex situ atomic force microscopy (AFM) scans of LB-transferred MGs at the air/solid interface reveal strong lateral 2D hexagonal ordering across a broad range of lateral surface pressures at the air/water interface before LB-transfer. Notably, for the first time, these results were confirmed by OSR, demonstrating the existence of the long-range hexagonal ordering at low and intermediate surface pressures. For in situ conditions and upon uniaxial compression at the air/water interface, the MG lattice constant decreases non-monotonically. This indicates the formation of domains at low pressures, that approach each other and only compress when the surface isotherm reaches a plateau. Comparing results of in situ and ex situ measurements, our study clearly shows a transfer effect during the LB-deposition on the lateral ordering of the MGs: The distance between the particles decrease during LB-transfer and at high pressures ($Π,>,22,mathrmmNm^-1$) a second distance occurs indicating small domains with hexagonal internal ordering. The novel surface characterisation approaches here highlight the use of both XRR and OSR to probe the vertical and lateral structure of adsorbed MGs, offering in situ, non-invasive insights without the need for doping or transfer-induced artefacts.
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
abstract = {The paper addresses the vertical and lateral structure of microgels (MGs) layers at the air/water interface and the effect of Langmuir-Blodgett (LB) transfer on solid substrates on the structure. The MGs are based on poly($N$-isopropylacrylamide) networks. For studying the structure at the air/water interface specular and off-specular X-ray reflectivity (OSR/XRR) allows in situ measurements without any labelling techniques. The initial ex situ atomic force microscopy (AFM) scans of LB-transferred MGs at the air/solid interface reveal strong lateral 2D hexagonal ordering across a broad range of lateral surface pressures at the air/water interface before LB-transfer. Notably, for the first time, these results were confirmed by OSR, demonstrating the existence of the long-range hexagonal ordering at low and intermediate surface pressures. For in situ conditions and upon uniaxial compression at the air/water interface, the MG lattice constant decreases non-monotonically. This indicates the formation of domains at low pressures, that approach each other and only compress when the surface isotherm reaches a plateau. Comparing results of in situ and ex situ measurements, our study clearly shows a transfer effect during the LB-deposition on the lateral ordering of the MGs: The distance between the particles decrease during LB-transfer and at high pressures ($Π,>,22,mathrmmNm^-1$) a second distance occurs indicating small domains with hexagonal internal ordering. The novel surface characterisation approaches here highlight the use of both XRR and OSR to probe the vertical and lateral structure of adsorbed MGs, offering in situ, non-invasive insights without the need for doping or transfer-induced artefacts.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
The paper addresses the vertical and lateral structure of microgels (MGs) layers at the air/water interface and the effect of Langmuir-Blodgett (LB) transfer on solid substrates on the structure. The MGs are based on poly($N$-isopropylacrylamide) networks. For studying the structure at the air/water interface specular and off-specular X-ray reflectivity (OSR/XRR) allows in situ measurements without any labelling techniques. The initial ex situ atomic force microscopy (AFM) scans of LB-transferred MGs at the air/solid interface reveal strong lateral 2D hexagonal ordering across a broad range of lateral surface pressures at the air/water interface before LB-transfer. Notably, for the first time, these results were confirmed by OSR, demonstrating the existence of the long-range hexagonal ordering at low and intermediate surface pressures. For in situ conditions and upon uniaxial compression at the air/water interface, the MG lattice constant decreases non-monotonically. This indicates the formation of domains at low pressures, that approach each other and only compress when the surface isotherm reaches a plateau. Comparing results of in situ and ex situ measurements, our study clearly shows a transfer effect during the LB-deposition on the lateral ordering of the MGs: The distance between the particles decrease during LB-transfer and at high pressures ($Π,>,22,mathrmmNm^-1$) a second distance occurs indicating small domains with hexagonal internal ordering. The novel surface characterisation approaches here highlight the use of both XRR and OSR to probe the vertical and lateral structure of adsorbed MGs, offering in situ, non-invasive insights without the need for doping or transfer-induced artefacts.
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Hayden Robertson; Joanne Zimmer; Anuar Sifuentes Name; Cassia Lux; Sebastian Stock; Regine Klitzing; Olaf Soltwedel
In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces Miscellaneous
2025.
@misc{https://doi.org/10.48550/arxiv.2503.14181iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii,
title = {In situ vs ex situ: Comparing the structure of PNIPAM microgels at the air/water and air/solid interfaces},
author = {Hayden Robertson and Joanne Zimmer and Anuar Sifuentes Name and Cassia Lux and Sebastian Stock and Regine Klitzing and Olaf Soltwedel},
url = {https://arxiv.org/abs/2503.14181},
doi = {10.48550/ARXIV.2503.14181},
year = {2025},
date = {2025-01-01},
publisher = {arXiv},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
2024
Hayden Robertson; Isaac J. Gresham; Andrew R. J. Nelson; Kasimir P. Gregory; Edwin C. Johnson; Joshua D. Willott; Stuart W. Prescott; Grant B. Webber; Erica J. Wanless
Solvent-Modulated Specific Ion Effects: Poly(N-isopropylacrylamide) Brushes in Nonaqueous Electrolytes Journal Article
In: Langmuir, vol. 40, no. 1, pp. 335-347, 2024, ISSN: 1520-5827.
@article{Robertson_2023,
title = {Solvent-Modulated Specific Ion Effects: Poly(N-isopropylacrylamide) Brushes in Nonaqueous Electrolytes},
author = {Hayden Robertson and Isaac J. Gresham and Andrew R. J. Nelson and Kasimir P. Gregory and Edwin C. Johnson and Joshua D. Willott and Stuart W. Prescott and Grant B. Webber and Erica J. Wanless},
url = {http://dx.doi.org/10.1021/acs.langmuir.3c02596},
doi = {10.1021/acs.langmuir.3c02596},
issn = {1520-5827},
year = {2024},
date = {2024-12-01},
journal = {Langmuir},
volume = {40},
number = {1},
pages = {335-347},
publisher = {American Chemical Society (ACS)},
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.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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.
Hayden Robertson; Isaac J. Gresham; Andrew R. J. Nelson; Stuart W. Prescott; Grant B. Webber; Erica J. Wanless
Illuminating the nanostructure of diffuse interfaces: Recent advances and future directions in reflectometry techniques Journal Article
In: Advances in Colloid and Interface Science, vol. 331, iss. 1, pp. 103238, 2024, ISSN: 0001-8686.
@article{Robertson_2024,
title = {Illuminating the nanostructure of diffuse interfaces: Recent advances and future directions in reflectometry techniques},
author = {Hayden Robertson and Isaac J. Gresham and Andrew R. J. Nelson and Stuart W. Prescott and Grant B. Webber and Erica J. Wanless},
url = {http://dx.doi.org/10.1016/j.cis.2024.103238},
doi = {10.1016/j.cis.2024.103238},
issn = {0001-8686},
year = {2024},
date = {2024-09-01},
journal = {Advances in Colloid and Interface Science},
volume = {331},
issue = {1},
pages = {103238},
publisher = {Elsevier BV},
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.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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.
Gareth R. Elliott; Kasimir P. Gregory; Hayden Robertson; Vincent S. J. Craig; Grant B. Webber; Erica J. Wanless; Alister J. Page
The known-unknowns of anomalous underscreening in concentrated electrolytes Journal Article
In: Chemical Physics Letters, vol. 843, pp. 141190, 2024, ISSN: 0009-2614.
@article{Elliott_2024,
title = {The known-unknowns of anomalous underscreening in concentrated electrolytes},
author = {Gareth R. Elliott and Kasimir P. Gregory and Hayden Robertson and Vincent S. J. Craig and Grant B. Webber and Erica J. Wanless and Alister J. Page},
url = {http://dx.doi.org/10.1016/j.cplett.2024.141190},
doi = {10.1016/j.cplett.2024.141190},
issn = {0009-2614},
year = {2024},
date = {2024-05-01},
journal = {Chemical Physics Letters},
volume = {843},
pages = {141190},
publisher = {Elsevier BV},
abstract = {Electrolytes are central to life and technology but lack complete understanding. Recent experiments with highly concentrated electrolytes have revealed electrostatic decay lengths orders of magnitude larger than those predicted by theory and simulation. This phenomenon, dubbed 'anomalous under-screening' and its origin is still lack a comprehensive understanding. Herein we provide a perspective over recent developments in this field and discuss phenomena that, while potentially pertinent to electrolyte underscreening, are yet to be fully explored-i.e. the 'known-unknowns' of electrostatic un-derscreening in concentrated electrolytes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Electrolytes are central to life and technology but lack complete understanding. Recent experiments with highly concentrated electrolytes have revealed electrostatic decay lengths orders of magnitude larger than those predicted by theory and simulation. This phenomenon, dubbed 'anomalous under-screening' and its origin is still lack a comprehensive understanding. Herein we provide a perspective over recent developments in this field and discuss phenomena that, while potentially pertinent to electrolyte underscreening, are yet to be fully explored-i.e. the 'known-unknowns' of electrostatic un-derscreening in concentrated electrolytes.
Isaac J. Gresham; Edwin C. Johnson; Hayden Robertson; Joshua D. Willott; Grant B. Webber; Erica J. Wanless; Andrew R. J. Nelson; Stuart W. Prescott
Comparing polymer-surfactant complexes to polyelectrolytes Journal Article
In: Journal of Colloid and Interface Science, vol. 655, pp. 262-272, 2024, ISSN: 0021-9797.
@article{Gresham_2024,
title = {Comparing polymer-surfactant complexes to polyelectrolytes},
author = {Isaac J. Gresham and Edwin C. Johnson and Hayden Robertson and Joshua D. Willott and Grant B. Webber and Erica J. Wanless and Andrew R. J. Nelson and Stuart W. Prescott},
url = {http://dx.doi.org/10.1016/j.jcis.2023.10.101},
doi = {10.1016/j.jcis.2023.10.101},
issn = {0021-9797},
year = {2024},
date = {2024-02-01},
journal = {Journal of Colloid and Interface Science},
volume = {655},
pages = {262-272},
publisher = {Elsevier BV},
abstract = {Hypothesis: Understanding the complex interactions between polymers and surfactants is required to optimise commercially relevant systems such as paint, toothpaste and detergent. Neutral polymers complex with surfactants, forming 'pearl necklace' structures that are often conceptualised as pseudo-polyelectrolytes. Here we pose two questions to test the limits of this analogy: Firstly, in the presence of salt, do these polymer-surfactant systems behave like polyelectrolytes? Secondly, do polymer-surfactant complexes resist geometric confinement like polyelectrolytes? Experiments: We test the limits of the pseudo-polyelectrolyte analogy through studying a poly(N-isopropylacrylamide) (PNIPAM) brush in the presence of sodium dodecylsulfate (SDS). Brushes are ideal for interrogating pseudo-polyelectrolytes, as neutral and polyelectrolyte brushes exhibit distinct and well understood behaviours. Spectroscopic ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), and neutron reflectometry (NR) were used to monitor the behaviour and structure of the PNIPAM-SDS system as a function of NaCl concentration. The ability of the PNIPAM-SDS complex to resist geometric confinement was probed with NR. Findings: At a fixed SDS concentration below the zero-salt CMC, increasing NaCl concentration <100 mM promoted brush swelling due to an increase in osmotic pressure, not dissimilar to a weak polyelectrolyte. At these salt concentrations, the swelling of the brush could be described by a single parameter: the effective CMC. However, at high NaCl concentrations (e.g., 500 mM) no brush collapse was observed at all (non-zero) concentrations of SDS studied, contrary to what is seen for many polyelectrolytes. Study of the polymer-surfactant system under confinement revealed that the physical volume of surfactant dominates the structure of the strongly confined system, which further differentiates it from the polyelectrolyte case.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hypothesis: Understanding the complex interactions between polymers and surfactants is required to optimise commercially relevant systems such as paint, toothpaste and detergent. Neutral polymers complex with surfactants, forming 'pearl necklace' structures that are often conceptualised as pseudo-polyelectrolytes. Here we pose two questions to test the limits of this analogy: Firstly, in the presence of salt, do these polymer-surfactant systems behave like polyelectrolytes? Secondly, do polymer-surfactant complexes resist geometric confinement like polyelectrolytes? Experiments: We test the limits of the pseudo-polyelectrolyte analogy through studying a poly(N-isopropylacrylamide) (PNIPAM) brush in the presence of sodium dodecylsulfate (SDS). Brushes are ideal for interrogating pseudo-polyelectrolytes, as neutral and polyelectrolyte brushes exhibit distinct and well understood behaviours. Spectroscopic ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), and neutron reflectometry (NR) were used to monitor the behaviour and structure of the PNIPAM-SDS system as a function of NaCl concentration. The ability of the PNIPAM-SDS complex to resist geometric confinement was probed with NR. Findings: At a fixed SDS concentration below the zero-salt CMC, increasing NaCl concentration <100 mM promoted brush swelling due to an increase in osmotic pressure, not dissimilar to a weak polyelectrolyte. At these salt concentrations, the swelling of the brush could be described by a single parameter: the effective CMC. However, at high NaCl concentrations (e.g., 500 mM) no brush collapse was observed at all (non-zero) concentrations of SDS studied, contrary to what is seen for many polyelectrolytes. Study of the polymer-surfactant system under confinement revealed that the physical volume of surfactant dominates the structure of the strongly confined system, which further differentiates it from the polyelectrolyte case.
2023
Anand Kumar; Vincent S. J. Craig; Hayden Robertson; Alister J. Page; Grant B. Webber; Erica J. Wanless; Valerie D. Mitchell; Gunther G. Andersson
Specific Ion Effects at the Vapor–Formamide Interface: A Reverse Hofmeister Series in Ion Concentration Depth Profiles Journal Article
In: Langmuir, vol. 39, no. 36, pp. 12618-12626, 2023, ISSN: 1520-5827.
@article{Kumar_2023,
title = {Specific Ion Effects at the Vapor–Formamide Interface: A Reverse Hofmeister Series in Ion Concentration Depth Profiles},
author = {Anand Kumar and Vincent S. J. Craig and Hayden Robertson and Alister J. Page and Grant B. Webber and Erica J. Wanless and Valerie D. Mitchell and Gunther G. Andersson},
url = {http://dx.doi.org/10.1021/acs.langmuir.3c01286},
doi = {10.1021/acs.langmuir.3c01286},
issn = {1520-5827},
year = {2023},
date = {2023-08-01},
journal = {Langmuir},
volume = {39},
number = {36},
pages = {12618-12626},
publisher = {American Chemical Society (ACS)},
abstract = {Employing neutral impact collision ion scattering spectroscopy (NICISS), we have directly measured the concentration depth profiles (CDPs) of various monovalent ions at the vapor-formamide interface. NICISS provides CDPs of individual ions by measuring the energy loss of neutral helium atoms backscattered from the solution interface. CDPs at the vapor-formamide interface of Cl-, Br-, I-, Na+, K+, and Cs+ are measured and compared to elucidate the interfacial specific ion trends. We report a reverse Hofmeister series in the presence of inorganic ions (anion and cation) at the vapor-formamide interface relative to the water-vapor interface, and the CDPs are found to be independent of the counterion for most ions studied. Thus, ions at the surface of formamide follow a "Hofmeister paradigm" where the counterion does not impact the ion series. These specific ion trends are complemented with surface tension and X-ray absorption near-edge structure (XANES) measurements on formamide electrolyte solutions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Employing neutral impact collision ion scattering spectroscopy (NICISS), we have directly measured the concentration depth profiles (CDPs) of various monovalent ions at the vapor-formamide interface. NICISS provides CDPs of individual ions by measuring the energy loss of neutral helium atoms backscattered from the solution interface. CDPs at the vapor-formamide interface of Cl-, Br-, I-, Na+, K+, and Cs+ are measured and compared to elucidate the interfacial specific ion trends. We report a reverse Hofmeister series in the presence of inorganic ions (anion and cation) at the vapor-formamide interface relative to the water-vapor interface, and the CDPs are found to be independent of the counterion for most ions studied. Thus, ions at the surface of formamide follow a "Hofmeister paradigm" where the counterion does not impact the ion series. These specific ion trends are complemented with surface tension and X-ray absorption near-edge structure (XANES) measurements on formamide electrolyte solutions.