Electrical and electrorheological behavior of poly(aniline-co-1,4-phenylenediamine) suspensions

Smart and Functional Conducting Polymers: Application to Electrorheological Fluids

Electro-responsive smart electrorheological (ER) fluids consist of electrically polarizing organic or inorganic particles and insulating oils in general. In this study, we focus on various conducting polymers of polyaniline and its derivatives and copolymers, along with polypyrrole and poly(ionic liquid), which are adopted as smart and functional materials in ER fluids. Their ER characteristics, including viscoelastic behaviors of shear stress, yield stress, and dynamic moduli, and dielectric properties are expounded and appraised using polarizability measurement, flow curve testing, inductance-capacitance-resistance meter testing, and several rheological equations of state. Furthermore, their potential industrial applications are also covered.

Core-Shell-Structured Copolyaniline-Coated Polymeric Nanoparticle Suspension and Its Viscoelastic Response under Various Electric Fields

Semi-conducting poly(n-methylaniline) (PNMA)-coated poly(methyl methacrylate) (PMMA) composite nanoparticles were synthesized using cross-linked and grafted PMMA particles as a core, and then, the PNMA shell was coated via chemical oxidative polymerization on the surface of modified PMMA nanoparticles. Their electroresponsive electrorheological characteristics when dispersed in silicone were confirmed under applied electric fields using a rotational rheometer, focusing on their viscoelastic response. Using a frequency sweep test, the frequency dependence of both the storage and loss moduli was confirmed to increase upon increasing the electric field, with a stable plateau regime over the entire angular frequency range.

Poly(phenylenediamine) Dispersions

The formation and properties of poly(phenylenediamine) colloidal dispersions were investigated. Oxidative dispersion polymerization of 1,3-phenylenediamine dihydrochloride stabilized with poly(N-vinylpyrrolidone) was taken as a reference experiment. Conductivity, temperature, and acidity of the reaction mixture were recorded during the polymerization. Oxidations of all three phenylenediamine bases, of corresponding dihydrochlorides, and of dihydrochlorides in excess acid are compared. The effect of the nature of steric stabilizer on the course of polymerization was found to be marginal. Dispersion polymerization was observed to proceed faster than the precipitation one. Dynamic light scattering was used to assess particle sizes in poly(phenylenediamine) dispersions. The results are discussed in relation to an analogous polymerization of aniline leading to polyaniline dispersions. Copyright 2001 Academic Press.