ORCID Profile
0000-0003-0653-1390
Current Organisation
The University of Newcastle
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Publisher: International Union of Crystallography (IUCr)
Date: 16-04-2021
DOI: 10.1107/S160057672100251X
Abstract: Neutron reflectometry is the foremost technique for in situ determination of the volume fraction profiles of polymer brushes at planar interfaces. However, the subtle features in the reflectometry data produced by these diffuse interfaces challenge data interpretation. Historically, data analyses have used least-squares approaches that do not adequately quantify the uncertainty of the modeled profile and ignore the possibility of other structures that also match the collected data (multimodality). Here, a Bayesian statistical approach is used that permits the structural uncertainty and multimodality to be quantified for polymer brush systems. A free-form model is used to describe the volume fraction profile, minimizing assumptions regarding brush structure, while only allowing physically reasonable profiles to be produced. The model allows the total volume of polymer and the profile monotonicity to be constrained. The rigor of the approach is demonstrated via a round-trip analysis of a simulated system, before it is applied to real data examining the well characterized collapse of a thermoresponsive brush. It is shown that, while failure to constrain the interfacial volume and consider multimodality may result in erroneous structures being derived, carefully constraining the model allows for robust determination of polymer brush compositional profiles. This work highlights that an appropriate combination of flexibility and constraint must be used with polymer brush systems to ensure the veracity of the analysis. The code used in this analysis is provided, enabling the reproduction of the results and the application of the method to similar problems.
Publisher: Elsevier BV
Date: 12-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2PY01487D
Abstract: Structural characterisation of thermoresponsive polymer brushes in binary DMSO–water mixtures reveals both LCST and UCST behaviour.
Publisher: Zenodo
Date: 2022
Publisher: American Chemical Society (ACS)
Date: 29-08-2023
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 04-2022
DOI: 10.1016/J.JCIS.2021.12.117
Abstract: Electrostatic extraction of particles from a bed to a pendent droplet to form liquid marbles has previously been investigated with respect to particle conductivity, size and shape, however, interparticle forces have not been specifically interrogated. If cohesion is the dominant force within the particle bed, then particles will be more readily extracted with reduced surface free energy. Glass particles were surface-modified using various alkyltrichlorosilanes. The surface free energy was measured for each s le using colloid probe atomic force microscopy (AFM) and sessile drop measurements on similarly modified glass slides. The ease of electrostatic particle extraction of each particle s le to a pendent droplet was compared by quantifying the electric field force required for successful extraction as a function of the measured surface free energy. Surface free energy calculated from sessile droplet measurements and AFM were not in agreement, as work of adhesion of a liquid droplet on a planar substrate is not representative of the contact between particles. Ease of electrostatic extraction of particles was observed to generally decrease as a function of AFM-derived surface free energy, confirming this is a critical factor in electrostatic delivery of particles to a pendent droplet. Roughness was also shown to inhibit particle extraction.
Publisher: Elsevier BV
Date: 03-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP02206D
Abstract: Hypersaline environments are ubiquitous in nature and are found in myriad technological processes. Recent empirical studies have revealed a significant discrepancy between the predicted and observed screening lengths at high...
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CP00847E
Abstract: This perspective reviews the historical explanations for specific ion effects, and explores the frontiers of the field before summarising its challenges and opportunities.
No related grants have been discovered for Hayden Robertson.