Scientists based at the University of Georgia, US, have grown conjugated polymer brushes directly onto monolayers, producing films with thicknesses less than 42 nanometres. This is a significant breakthrough for nanotechnology as existing techniques for creating electronics on the nanoscale are reaching their limits.    

Previous attempts to grow conjugated polymers on monolayers have had limited success. Using a modified Kumada-type catalyst-transfer polycondensation, Jason Locklin and his team grew polyphenylene and polythiophene brushes, from aryl Grignard monomers, on gold monolayers. They analysed the polymer brushes using cyclic voltammetry, polarization modulation-infrared reflection-adsorption spectroscopy and atomic force microscopy. 'This surface-initiated polymerisation technique allows one to create conjugated polymer films in a controlled fashion,' Locklin comments. The technique 'allows for a high density of functional groups to be obtained in a limited area. This has been called the skyscraper approach.' 

'Locklin's work represents another important addition to the synthetic toolbox for generating functional polymer brushes,' says Wilhelm Huck, an expert in macromolecular chemistry at the University of Cambridge, UK. 'I am confident that we will see a lot more work on conjugated polymer brushes and with improvements in synthesis, hopefully, improvements in device performance will follow.' 

With potential applications in electroluminescent and photoelectric devices, batteries and organic electronics, it may be difficult to know which to study further. Locklin sees his polymer brushes being used for the construction of enzymatic biofuel cells for powering cochlear implants and pacemakers, and biochemical sensors. 'Individual polymer chains serve as molecular wires, facilitating efficient charge transport between a fuel cell catalyst and the electrode to which it is attached,' he says. He is, however, realistic: 'There are many issues that must be overcome before this technique can be applied to real-world devices.'   

Ian Coates 

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