Electrochemical and Raman spectroelectrochemical investigation of single-wall carbon nanotubes–polythiophene hybrid materials

Two types of polythiophene—single-wall carbon nanotubes (SWCNTs) composites are comparatively studied. Composites of the first type consisted of nonmodified SWCNTs and nonmodified regioregular poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene) (P3OT) or poly(dioctylterthiophenes) (PDOTT). Composites of the second type (molecular composites) were obtained by grafting carboxylic acid functionalized poly(alkylthiophene)s on amine functionalized SWCNTs. In AFM images of the composites of nonfunctionalized components, individual carbon nanotubes can be easily distinguished, which are well dispersed in the polymer matrix showing fibrilar morphology. Cyclic voltammetry and Raman spectroelectrochemical experiments unequivocally show that all characteristic redox and spectroscopic features of both SWCTs and the polymer are retained in the composite material. Moreover the percolating network of SWCTs facilitates the electrochemical doping of the polymeric component. These new, solution processible materials are good candidates for printable contact electrodes in organic electronics. Molecular composites obtained by grafting show a different morphology. It is characterized by a network of fibers of diameters ranging from few dozens to few hundreds nm. Individual composite components cannot be distinguished which is an obvious consequence of the grafting reaction. Combined voltammetric and Raman spectroelectrochemical studies show that the grafting reaction lowers the electrochemical activity of the polymer component and the resulting maximum doping level is, in this case, lower than that found in composites of nonmodified components.