Synthesis and characterization of polyaniline membranes with – secondary amine additive containing N,N′-dimethyl propylene urea for fuel cell application

In this study, the self-standing membranes of polyaniline (PANI) containing N,N′-Dimethyl propylene urea – were prepared by solution cast method followed by protonation with concentrated hydrochloric acid. The secondary amine i.e. heptamethyleneimine was used as a gel inhibitor, and to stabilize the PANI in N,N′-dimethyl propylene urea solution. Different physicochemical techniques such as X-ray Diffractometry, Fourier transform infrared spectroscopy, and scanning electron microscopy were used for the characterizations of membranes. X-ray study shows that crystallinity of protonated PANI membrane was higher than that of non-protonated membrane. The non-protonated PANI membrane had only short fibers. However, protonated membrane also had long fibers/or bunch of fibers along with short fibers. Secondary amines with moderate or strong basicity, reduce most of the quinoid ring to form a ring-substituted material because of which materials conjugated structure was degraded. The DC electrical conductivities of the membranes were evaluated with an electrometer. It has been observed that protonated PANI membrane was electrically more conducting as compared to non-protonated membrane. The electrical conductivity of non-protonated and protonated PANI membranes upto 4 V was 5.95 μS/cm and 6.73 μS/cm, respectively and beyond that, it increased to 7.29 μS/cm and 8.45 μS/cm. The protonated PANI membranes with higher electrical conductivity could be useful for the hydrogen fuel cell application.