Conducting Polymers Research
- Polythiophene derivatives for biosensing.
- New approaches to the synthesis of regioregular polyalkylthiophenes.
- Polythiophenes with covalently-attached metal complexes.
1. Polythiophene derivatives for biosensing
Collaborators: Andrew Cossins (Liverpool).
As a ‘proof of principle’ experiment, we made electrochemically-deposited polythiophenes with covalently-attached biochemical binding sites such as biotin (a small molecule that strongly and specifically binds to a protein called avidin), and oligonucleotides (short lengths of single-stranded DNA). We showed that we could use changes in the electrochemical response of these polymers on binding to detect avidin, or complementary DNA strands, respectively1,2.
Later, we extended this work to PEDOT derivatives and showed that with the latter, we could use microelectrodes (20 µm disk electrodes) successfully (something that was impossible with other conducting polymers) because of the unique fibrillar morphology of PEDOT polymers. This enabled us to cut the detection limit for electrochemical oligonucleotide detection by over 3 orders of magnitude3,4. This work was patented5.
Publications
| 1. A regioregular polyalkylthiophene bearing covalently-linked biotin, and its interaction with avidin in solution and in thin films |
| F. Mouffouk, S.J. Higgins, S.J. Brown, N. Sedghi, W. Eccleston and S. Reeman |
| Chemical Communications, 2004, 2314-2315. |
| 2. Electrosynthesis and characterization of biotin–functionalized poly(terthiophene) copolymers, and their response to avidin |
| F. Mouffouk, S.J. Brown, A.M. Demetriou, S.J. Higgins, R.J. Nichols, R.M.G. Rajapakse and S. Reeman |
| Journal of Materials Chemistry,2005, 15, 1186–1196. |
| 3. A biotin-functionalised poly(3,4-ethylenedioxythiophene)-coated microelectrode which responds electrochemically to avidin binding |
| M. Fouzi and S.J. Higgins |
| Electrochemical Communications, 2006, 8, 15-20. |
| 4. Oligonucleotide-functionalised poly(3,4-ethylenedioxythiophene)-coated microelectrodes which show selective electrochemical response to hybridisation |
| M. Fouzi and S.J. Higgins |
| Electrochemical Communications, 2006, 8, 317-322. |
5. Patents
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2. New approaches to the synthesis of regioregular polyalkylthiophenes
Collaborators: Martin Heeney and Iain McCulloch (Both originally at Merck Chemicals, Southampton)
So-called ‘regioregular’ polyalkylthiophenes are important polythiophene derivatives because they have excellent solid-state electrical properties that are a consequence of the self-assembly of polythiophene chains. There is a lot of interest in developing new synthetic routes to this class of materials. In particular, it would be of interest to develop functional group-tolerant chemistry that would allow the attachment of interesting substituents to the alkyl chains, or permit the synthesis of less electron-rich polymers with similar self-assembly properties. We have shown that C-H activation borylation followed by palladium-catalysed coupling can be used to make regioregular polyalkylthiophenes without the use of any strong bases such as organolithium reagents1.
| 1. Suzuki route to regioregular polyalkylthiophenes using Ir–catalysed borylation to make the monomer, and Pd complexes of bulky phosphanes as coupling catalyst for polymerisation |
| I.A. Liversedge, S.J. Higgins, M. Giles, M. Heeney and I. McCulloch |
| Tetrahedron Letters,2006, 47, 5143-5146. |
3. Polythiophenes with covalently-attached metal complexes
We have synthesised metal complexes that have one or more thiophene unit(s) as substituents, and we have used electrochemical oxidation of these molecules to deposit films of conducting polythiophenes on electrode surfaces. Potentially, this is a way of depositing an electrocatalyst, held within a conducting matrix, onto an electrode surface. Examples we have studied include metal-tetraazamacrocycle complexes embedded in polythiophene1. More recently, we have turned to poly-(3,4-ethylenedioxythiophene) (PEDOT) derivatives, because these polymers are particularly stable to redox cycling and are conducting at very mild potentials. We have made PEDOTs containing both redox-active metal-tetraazamacrocycle complexes2,3 and potentially catalytic metal-phosphine complexes4 (the first time that this had been achieved for a polythiophene derivative).
A polythiophene containing [Ni(cyclam)]2+. Both the polymer and the metal complex are reversibly redox-active in these materials1.
A 3,4-ethylenedioxythiophene derivative with a [Ni(cyclam)]2+ substituent. PEDOT polymers were prepared electrochemically from this and related molecules2,3.
A square planar Pt(II) complex of an EDOT-bearing phosphine ligand. We found that we could make PEDOT materials using such monomers, while maintaining the Pt(II) complex intact in the resulting polymer4.
| 1. Syntheses and electro(co)polymerization of novel thiophene– and 2,2’:5’,2’’–terthiophene–functionalized metal–tetraazamacrocycle complexes, and electrochemical and spectroelectrochemical characterization of the resulting polythiophenes |
| S.J. Higgins, T.J. Pounds and P.A. Christensen |
| Journal of Materials Chemistry,2001, 11, 2253-2261. |
| 2. A [Ni(cyclam)]2+ –functionalised poly(3,4–ethylenedioxythiophene): synthesis, electropolymerisation and characterisation of the polymer by cyclic voltammetry and in situ reflectance FTIR spectroscopy |
| R.M.G. Rajapakse, S.J. Higgins and K. Velauthamurty |
| Inorganica Chimica Acta, 2006, 359, 3491-3496. |
| 2. Synthesis and characterization of monomeric and polymeric Cu(II) complexes of 3,4-ethylenedioxythiophene functionalized with cyclam ligand |
| F. Mouffouk, A. Demetriou, S.J. Higgins and R.J. Nichols |
| Electrochimica Acta, 2010, 56, 326-332. |
| 2. Synthesis and characterization of monomeric and polymeric Pd(II) and Pt(II) complexes of 3,4–ethylenedioxythiophene–functionalized phosphine ligands |
| K. Velauthamurty, S.J. Higgins, R.M.G. Rajapakse, J. Bacsa, H. van Zalinge, R.J. Nichols and W. Haiss |
| Journal of Materials Chemistry, 2009, 19, 1850-1858. |
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