Structural, Thermal and Electrochemical Behavior of Poly(2-ethylaniline)-nanocomposite-Fe2O3 and Poly(2-ethylaniline)-nanocomposite-SiO2 for Antibacterial and Antioxidant Studies

Poly(2-ethylaniline) (PEAN), poly(2-ethylaniline)-nanocomposite-Fe₂O₃ (PEAN/Fe₂O₃) and poly(2-ethylaniline)-nanocomposite-SiO₂ (PEAN/SiO₂) are synthesized by emulsion polymerization and characterized by UV–Visible, FTIR spectroscopy, Powder XRD, TGA, DTA, and SEM-EDX. The nanocomposites are amorphous and exhibit a three-step thermal degradation corresponding to the loss of moisture, loss of dopant, and the decomposition of the polymer composites. The electrical conductivity of the semi-conducting emeraldine salt forms of PEAN, PEAN/Fe₂O₃ and PEAN/SiO₂ doped with chloride ions and camphor sulphonate ions are 4.3 × 10^–4, 3.6 × 10^–5, and 4.8 × 10^–3 S/cm respectively. PEAN, PEAN/Fe₂O₃ and PEAN/SiO₂ show excellent antibacterial activity against the gram-positive bacteria Staphylococcus aureus, moderate activity against Salmonella typhi and Klebsiella pneumoniae, and weak activity against Bacillus subtilis and Enterococcus faecalis. These materials are inactive against Escherichia coli. The destruction of the bacterial cell membranes due to the stronger interaction between the doped polycation chains and the negatively charged bacterial cell wall, and the release of Fe³⁺ ions due to electrostatic interaction facilitates the binding to the negatively charged bacterial cell membrane. The large surface area and the high content of SiOH groups in nanoporous silica facilitates the attachment with the surface of the bacterial cell walls. The nanocomposites demonstrate relatively good free radical scavenging activity at a concentration of 50 µL.