Aniline-oriented polymerization over nano-SiO2 particles

The goal of this paper is to report a systematic structural and morphological characterization of PANI-ES/nano-SiO2 hybrid composite, which was synthesized in the bulk form by surface modification of nano-SiO2 particles through in situ polymerization of aniline. The aniline-oriented polymerization was observed. XRD patterns of Polyaniline Emeraldine-salt form (PANI-ES) and PANI + nano-SiO2 nanocomposite showed some differences. The intensities of peaks indexed as (1 1 0) and (4 3 0) decreased after polymerization in the nanocomposite form, while the intensities of the peaks (4 0 0), (0 0 1) and (0 3 0) remain unchanged. The unchanged planes are parallel to the unit cell axis and therefore parallel to the polymeric chains. This fact clearly indicates an oriented polymerization of aniline over the nano-SiO2 particles. SEM images showed that the nanocomposite is made up of PANI-ES nanofibers deposited over the nano-SiO2 particles. Furthermore, the PANI-ES morphology remains unchanged after polymerization in the presence of nano-SiO2 particles. The theoretical quantum chemical calculations were performed to verify the effect of successive deposition of PANI on the regular SiO2 surface. The participation of SiO2, although weak, occurs in most of the vibrational modes. Furthermore, the MEPS of SiO2 presents medium values of electrostatic potential, but of a mostly positive character, favoring the interaction with the polymer. The DC electrical conductivity of PANI-ES + nano-SiO2 composite was found around 1.22 × 10−4 S cm−1 at 25 °C, which is 10% higher than pure polyaniline prepared under the same polymerization conditions. The better-aligned polyaniline chains over the nano-SiO2 particles may improved the charge mobility along the polymer chains.