Relation between the morphology and electric conductivity of PADB/PHS blends prepared in different organic solvents

Blending is a promising approach, in the conducting polymer field, for taking advantage of the good mechanical properties and processability of conventional polymers. The challenge of producing blends with conducting polymer has been studied by many researchers in the last years. In this work, flexible and conducting films were obtained by casting poly(p-hydroxystyrene) (PHS) and doped polyaniline (PADB) mixtures from N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP) solutions. Freestanding films of blends were obtained by casting, which were characterized by conductivity measurements, optical microscopy (OM) and scanning electron microscopy (SEM). The conducting PADB/PHS blends, prepared from NMP, showed values of normalized conductivity from 10^-7 to 10^-6 S/cm for the compositions from 30 to 100 wt% of PADB. Compared to blends prepared from DMF solution, a reduction in the conductivity was observed for the present blends, prepared from NMP, for instance, the 50/50 PADB/PHS blends has shown conductivities of 10^-3 S/cm and 10^-7 S/cm, respectively. Morphology studies showed no separation of phases up to 70 wt% of PADB by OM and a homogeneous surface film by SEM, for the PADB/PHS 70/30 prepared from NMP solution. On the other hand, the PADB/PHS blends prepared from DMF solution showed the presence of aggregates, which could be observed using an OM and a fibrilar morphology by SEM. Conductivity represented a balance between PADB content and morphology of polymer blends.