ИСТИНА

The effects of the nanostructure of electrochemically deposited conducting polymer films on their redox behaviour is analyzed using poly(2,2’-bithiophene) (PBT) as an example. Two main phenomena are highlighted: (i) the effect of the deposition parameters on the nanostructure and redox properties, and (ii) the effect of the nanostructure on the dopant ion penetration and nanoscale doping level distribution in doped conducting polymer films as revealed by atomic force microscopy (AFM) and related techniques. In particular, using current-sensing AFM, we show that doped polymer samples feature nanoscale conductivity distribution that is opposite to that found by us earlier in undoped polymers [1]. Specifically (Fig. 1), while polymer grains still had a complex distribution of nanoscale conductivity, the most conducting areas were located now at the grain periphery, whereas the grain cores remained relatively less doped and less conducting. This fact was related to a higher degree of disorder typical for polymer grain periphery, as was demonstrated in our earlier works [1-3]. More disordered polymer is less rigid and is more susceptible to the dopant and solvent penetration and the associated swelling-deswelling. As a result, the disordered periphery is doped more easily and is found to be more conducting. On the contrary, dense and partially crystalline grain cores remain relatively undoped, as is seen from the nanoscale CS-AFM image (Fig. 1). When the polymer is undoped, the grain periphery is again undoped more easily, which renders the grain periphery less conducting than the grain cores in undoped polymers. Acknowledgements This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundation for Innovation/Ontario Innovation Trust (CFI/OIT), Ontario Centres of Excellence (OCE) and the Academic Development Fund of the University of Western Ontario. References 1) K.D. O'Neil, B. Shaw, O.A. Semenikhin, J. Phys. Chem. B 111 (2007) 9253 2) K.D. O'Neil, O.A. Semenikhin, J. Phys. Chem. C 111 (2007) 14823 3) O.A. Semenikhin, Annu. Rep. Prog. Chem., Sect. C: Phys.Chem., 106 (2010) 163