Thermoresponsive polyaniline nanoparticles: Preparation, characterization, and their potential application in waterborne anticorrosion coatings

Abstract Stable dispersions of polyaniline nanoparticles (PANI-NPs) were obtained from an oxidation polymerization of anilines in water with thermoresponsive poly(vinyl alcohol) (PVA) conjugated with 2-isobutyramidopropanoate moieties (PVA-AI) as the dispersing agent. UV–vis spectra, transmission electron microscopy, and dynamic light scattering (DLS) verified the formation of PANI-NPs. Compared with the PANI-NPs stabilized by PVA, PVA-AI was better at homogeneously dispersing PANI-NPs in water. Temperature-dependent UV–vis and DLS measurements demonstrated that the PANI-NP/PVA-AI composites were thermoresponsive in water. This was also evident from the turbid aqueous solutions at temperatures above the cloud point temperature ( T cp ). The T cp could be modulated by employing PVA-AI with different T cp or adding inorganic salts. Varying the pH below 5 had almost no influence on the T cp ; however, raising the pH above 5 lowered the T cp . Cyclic voltammetry analysis demonstrated that the PANI-NP/PVA-AI composites were electroactive and their redox process was repeatable. The T cp values of the composites in oxidation and reduction states were similar. Such thermoresponsive PANI-NP/PVA-AI composites were used as functional additives to improve the anticorrosive performance of waterborne epoxide coating films. After 460 h of harsh salt-spray corrosion, corrosion evaluation around the scribe, adhesion tests, potentiodynamic polarization measurement, electrochemical impedance spectroscopy measurement, and scanning electron microscope observation demonstrated that the anticorrosion performance of the epoxide coating containing thermoresponsive PANI-NP/PVA-AI was better than those with pure epoxide coating or epoxide coating containing PANI-NP/PVA without thermoresponsive properties.