The role of intermolecular interactions in polyaniline/polyamide-6,6 pressure-sensitive blends studied by DFT and 1H NMR

Abstract

The aim of this work was to understand the electrical-mechanical response of polyaniline-thermoplastic blends measured under dynamic conditions and to evaluate the effectiveness of this conducting blend as a pressure sensor. The studied composite materials were based on conducting blends composed of polyaniline, as the conducting phase, dispersed into an insulating thermoplastic polymer, polyamide-6,6. The compression sensitivity (conductivity changes response) of these materials was investigated. The range of polyaniline content in the studied blends was from 50 to 92wt.%, as estimated from melting enthalpies of temperature-modulated differential scanning calorimetry measurements. PA-6,6/PAni blend with 92wt.% PAni showed the highest electrical conductivity (6×10−5Scm−1) due to the presence of positively charged nitrogen atoms (N+) evidenced by XPS, as well as the highest compression sensitivity (25%MPa−1), attributed to the interconnected conducting network formed in PAni phase, as disclosed by SEM images.The first-principles calculations based on the density functional theory (DFT) were used to describe the interactions between NHCO and HNphenyl segments of the PA-6,6 and PAni chains, respectively. 1H Nuclear Magnetic Resonance spectra showed good agreement with the theoretical model through the observation of chemical shifts related to the chemical interaction between H from amine-N of PAni and carbonyl groups of PA-6,6.