Renewable Energy Global Innovations features: Electrochemically-controlled grafting of hydrophilic brushes from conducting polymer substrates

Significance Statement

Graft copolymers with a conducting polymer backbone are a promising class of material for the design of functional surfaces. Such materials are particularly well-suited to organic electronics applications such as polymer solar cells. This class of graft copolymer takes advantage of the electroactivity and optical properties of the conducting polymer backbone, with grafted sidechains selected to impart desired chemical, mechanical, and/or physical properties.[1–6]

Electrochemically-mediated ATRP (eATRP) has emerged in recent years as an alternative controlled radical polymerisation technique that utilises low concentrations of copper-based ATRP catalysts, and that can be conducted in the presence of atmospheric oxygen.[17–20]   We have adapted this versatile new technique to perform surface-initiated electrografting directly from a conducting polymer-functionalised substrate that acts as both a macroinitiator for polymer brush grafting, and as the working electrode to control catalyst oxidation state, and thereby catalyst activity. This new method of surface-initiated grafting from conducting polymer, once optimised, could provide a versatile tool for the synthesis of thin film polymer electronics with a high level of control over architecture and chemistry.

References:

[1] C.-H. Lin, W.-J. Chou, J.-T. Lee, Macromol. Rapid Commun. 2012, 33, 107–113.[2] M. F. Abasıyanık, M. Şenel, J. Electroanal. Chem. 2010, 639, 21–26.[3] Y. Yagci, L. Toppare, Polym. Int. 2003, 52, 1573–1578.[4] C. D. Grande, M. C. Tria, G. Jiang, R. Ponnapati, Y. Park, F. Zuluaga, R. Advincula, React. Funct. Polym. 2011, 71, 938–942.[5] L. T. Strover, J. Malmström, O. Laita, J. Reynisson, N. Aydemir, M. K. Nieuwoudt, D. E. Williams, P. R. Dunbar, M. A. Brimble, J. Travas-Sejdic, Polymer. 2013, 54, 1305–1317.[6] Y. Pei, J. Travas-Sejdic, D. E. Williams, Langmuir 2012, 28, 8072–8083.[7] N. Bortolamei, A.A. Isse, A.J.D. Magenau, A. Gennaro, K. Matyjaszewski, Angew. Chemie. 2011, 123, 11593–11596.[8] A. Magenau, N. Strandwitz, A. Gennaro, K. Matyjaszewski, Science 2011, 332, 81–84.[9] S. Park, H. Cho, K. Wegner, Macromolecules 2013, 46, 5856–5860.[10] A.J.D. Magenau, N. Bortolamei, E. Frick, S. Park, A. Gennaro, K. Matyjaszewski, Macromolecules, 2013, 46, 4346–4353. 

About The Author

Lisa T. Strover joined the Alexandre Yersin Department of Solar Energy and Environmental Physics (YDSEEP) at the Ben-Gurion University of the Negev, Israel, in June 2016. She completed her BSc(Hons) (2010) and Ph.D. (2016) in Chemistry within the Polymer Electronics Research Centre at the University of Auckland, with her research focusing on electroactive graft copolymer brushes for functional surfaces and electrochemically mediated ATRP from conducting polymer substrates.

About The Author

Jenny Malmström joined the Department of Chemical and Materials Engineering at the University of Auckland as a Lecturer in 2016. She received her MSc degree in Bioengineering at Chalmers University of Technology, Gothenburg, Sweden (2004) and a Ph.D. in Nanoscience at the University of Aarhus, Denmark (2010). From Denmark she moved to Auckland, where she joined the School of Chemical Sciences (UoA) as a post doctoral research fellow. Her research focuses on creating functional biointerfaces to understand and control biological systems.

About The Author

Jadranka Travas-Sejdic is a Professor at the School of Chemical Sciences, Director of the Polymer Electronics Research Centre at the University of Auckland, and a principal investigator at the MacDiarmid Institute for Advanced Materials and Nanotechnology. Her research interests are in the fields of advanced polymeric materials for biosensing and bioelectronics, electrically and environmentally responsive polymers and surfaces, actuators, materials for tissue engineering and nanostructured conducting polymers. She has (co)authored over 200 publications, including eight book chapters. 

Journal Reference

Electrochimica Acta, Volume 188,  2016, Pages 57–70.

Lisa T. Strover^1,2, Jenny Malmström^1,2, Louise A. Stubbing¹, Margaret A. Brimble^1,2, Jadranka Travas-Sejdic^1,2 

Show Affiliations

1. Polymer Electronics Research Centre, School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
2. MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand  

Abstract

Electrochemically-mediated ATRP (eATRP) has emerged in recent years as an alternative controlled radical polymerisation technique that utilises low concentrations of copper-based ATRP catalysts, and that can be conducted in the presence of atmospheric oxygen. In this work, we adapt eATRP to perform surface-initiated electrografting directly from a conducting polymer (CP) macroinitiator that also acts as the working electrode to control catalyst oxidation state, and thereby catalyst activity. Aqueous electrografting of hydrophilic poly(2-hydroxyethyl methacrylate) polymer brushes from the conducting polymer macroinitiator, in the presence of an ATRP catalyst (CuBr₂/TPMA), was confirmed by ATR-FTIR, water contact angle measurements, and XPS. Optimised grafting conditions were determined whereby polymerisation kinetics approached first order characteristics, as expected for grafting via an eATRP mechanism. However, even under these optimised conditions, we determined that competing electrografting mechanisms were likely occurring, with experiments supporting the occurrence of polymerisation in solution, followed by ‘grafting to’ reactions, as previously described for electrografting via surface electro-initiated emulsion polymerisation (SEEP). Additionally, spectroelectrochemical studies suggest that the mechanism of initiation differs from previously reported eATRP systems in that the conducting polymer itself acts as a co-reductant for the catalyst. As expected, the prevalence of uncontrolled grafting, due to competing grafting mechanisms, as well as effects such as chain termination and degrafting, was highly dependent on polymerisation conditions, most notably on the applied potential.

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