Preparation and characterization of nanofibers of polyvinyl alcohol/polyaniline-montmorillonite clay

This work describes the preparation of polyvinyl alcohol/polyaniline-montmorillonite clay (PVA/PANI-OMMT) nanofibers through electrospinning. Initially, for improving the compatibility of the clay towards the organic polymer, the montmorillonite (MMT) was submitted to an organophilization process using hexadecyltrimethylammonium bromide (CH3(CH2)15N(Br)(CH3)3). The PANI-OMMT composite, which was obtained after the in situ polymerization of aniline in presence of the organophilic clay (ratio of ≈1:3 in weight), was then placed in a matrix of PVA (weight ratio of 1:7 of composite:PVA) for the production of the PVA/PANI-OMMT composite fibers through electrospinning. We used several characterization techniques (X-ray diffraction (XRD); infrared absorption spectroscopy (FTIR), ultraviolet visible absorption spectroscopy (UV–Vis), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS)) to analyze the different samples produced. The clay organophilization was confirmed after observing the (001) plane displacement from 5,6° to 4,7° and absorption bands in 2924 cm−1, 2853 cm−1 and 1479 cm−1, as analyzed by XRD and FTIR, respectively. The presence of polyaniline in its emeraldine salt was identified by the presence of the characteristic UV–Vis absorption bands in 360 nm, 430 nm and 822 nm, while the formation of the PANI/OMMT nanocomposite was confirmed by observing the characteristic FTIR bands of each individual component. From the SEM images, we could establish that the resulting nanocomposite mats were composed by uniform fibers with an average diameter of 240 nm and presented good surface quality. We have found that EIS is an efficient technique for the evaluation of changes in the electric properties of the nanofibers after their exposure to vapors of methanol. We suggest that this organic-inorganic composite may find useful applications in the preparation of several devices based on polymers, such as heavy metal filtration membranes and gas sensors.