Inducing conductivity in immiscible PS/PP blends by a percolated polyaniline/PA filler selectively localised by specific interactions

We describe an approach to develop conducting immiscible blends of polystyrene (PS) and polypropylene (PP) with a percolated polyaniline/polyamide (PANI/PA) filler in the presence of a SEBS-g-MA compatibilizer. The underlying principle of the work is the ability of the compatibilizer to concurrently stabilize the bi-phasic morphology to develop co-continuous blends and to improve the dispersion of the filler by specific interactions. From the latter perspective, we have chosen a percolated composite of PANI in PA as the filler and prepared its master batches with the compatibilizer expecting that specific interactions between the amino end groups of PA and the MA anhydride groups in SEBS-g-MA would result in a better dispersion of PANI. The effect of master batch preparation method using either melt mixing or solution casting on the conductivity was studied, and the latter technique was found to be superior. As a result, the concomitant effect of morphology stabilization with improved PANI dispersion led to an improved connectivity of PANI in the phase of the blend where it selectively localizes (PS) for 40/60 PS/PP blends. To further improve the connectivity of PANI, we studied the effect of different sequence additions of the solution casted master batch to the blend components. Melt mixing the solution casted master batch with PS followed by PP resulted in double percolated PANI selectively localized in the continuous PS phase owing to their specific interaction in 50/50 PS/PP blend. This resulted in an increase of the dc conductivity by 6 decades in comparison to the neat blend, already at low PANI concentrations (6 wt%). The connectivity of the blend was affirmed by the power law behavior of the viscoelastic response, more in particular the storage modulus G', of the percolated blends. Furthermore, the effect of the compatibilized blend morphology on the dc conductivity and viscoelastic response was investigated by varying the blend composition. In summary, the proper choices of using a master batch preparation technique by solution casting and subsequently melt mixing the master batch with the polar PS phase followed by PP led to the formation of a double percolated network of filler in the continuous PS phase at low PANI concentrations.