Polymer Brushes Grafted from Conducting Polymer Backbones for Functional Materials

Abstract

Grafted conducting polymers (CPs) are a unique class of materials, combining the electrochemical and optical properties of the CP backbone with the desirable physical and chemical properties of the grafted polymer chains. This provides an almost infinite array of possibilities for tailored functional materials, with potential applications ranging from tissue culture substrates and biomedical devices to organic electronics and energy technology. The research in this thesis explores some of these possibilities, beginning with an investigation into the polymerisation of a relatively unknown CP containing sites for grafting. Building on this backbone, two novel grafted materials were fabricated, tailored towards cell culture applications and hydrogen generation respectively. Firstly, a suitable CP monomer was synthesised, based on 3,4-ethylenedioxythiophene (EDOT) and containing an initiating site for grafting via ATRP (atom transfer radical polymerisation). The electropolymerisation of this monomer, (3,4-ethylenedioxythiophene) methyl 2-bromopropanoate (BrEDOT), was then investigated to optimise the polymerisation parameters. In order to produce CP films with good adherence to the underlying electrode, an adhesion layer of PEDOT was required, with a layer of PBrEDOT or P(EDOT-co-BrEDOT) polymerised on top. These CP films were used as a macroinitiator to graft chains of poly(poly(ethyleneglycol)methyl ether methacrylate) (P(PEGMMA)), a well-characterised thermoresponsive polymer. These P(PEGMMA) brushes could be reversibly collapsed and swollen by changing either temperature or salt concentration, with corresponding changes in electrochemical and anti-biofouling properties. This switching behaviour holds great potential for a tissue culture substrate, with the ability to modulate cell adhesion and deliver electrochemical signals to the growing cells. Finally, a catalyst for hydrogen generation was fabricated from PBrEDOT grafted with poly(acrylic acid) (PAA) brushes and decorated with platinum nanoparticles (PtNPs). This novel grafted CP/PtNP system showed good catalytic activity towards the hydrogen evolution reaction (HER), performing on par with several previously-reported HER catalysts. The PtNPs appeared to be synergistically enhanced by the presence of PAA, indicating that this fabrication approach could be a powerful tool in reducing Pt loadings while increasing catalyst efficiency.