Wednesday, 20 October 11:00am – 12:00pm

This seminar will be delivered via Zoom – Please email chemistry.researchsupport@sydney.edu.au for zoom link and password.

Speaker: Professor Erica Wanless; University of Newcastle

Host: Dr Derrick Roberts

Title: How Polymer Brushes Behave in Complex Environments

Abstract: Polymer brushes are routinely grown from solid substrates to change surface behaviour to suit particular applications. In many instances these properties, such as wettability, lubricity, adhesion and even anti-fouling, are related to the nanostructure of the brush. We have demonstrated brush structure can be finely tuned by varying solution pH, temperature or salt concentration and identity independently.^1,2 However, reports on the influence of mixed aqueous electrolytes and nonaqueous electrolytes on the behaviour of polymer brushes are limited, as there is, to date, no all-inclusive theory regarding specific ion effects. As natural environments and advanced technologies are often comprised of complex electrolytes and/or nonaqueous electrolytes, understanding the interplay of different ions in various solvents is imperative for advancing our knowledge of polymer-salt interactions.

Subtle conformational changes in thermoresponsive polymer brushes have been used as exemplar systems to study specific ion effects.² These brushes undergo a phase transition from well to poorly solvated over a given temperature range, forming an interface with switchable physicochemical properties. Examples will be discussed from our recent studies of poly(N-isopropylacrylamide) and poly(oligo(ethylene glycol) methacrylate) brushes exposed to mixed electrolytes from across the Hofmeister series,^3,4 and also to nonaqueous electrolytes which also exhibit specific ion phenomena as we strive to further our understanding of these ubiquitous phenomena.

References

1. J. Willott, et al., Physicochemical behaviour of cationic polyelectrolyte brushes, Prog. Polym. Sci., 64, 52 (2017). DOI: 10.1016/j.progpolymsci.2016.09.010
2. T. Murdoch, et al., Specific ion effects on thermoresponsive polymer brushes: Comparison to other architectures, J. Colloid Interface Sci., 526, 429 (2018). DOI: 10.1016/j.jcis.2018.04.086
3. E. Johnson, et al., Temperature dependent specific ion effects in mixed salt environments on a thermoresponsive poly(oligoethylene glycol methacrylate) brush, Phys. Chem. Chem. Phys., 21, 4650 (2019). DOI: 10.1039/C8CP06644B
4. H. Robertson, et al., Competitive specific ion effects in mixed salt solutions on a thermoresponsive polymer brush, J. Colloid Interface Sci., 586, 292 (2021). DOI: 10.1016/j.jcis.2020.10.092