Synthesis and electrorheological characteristics of microencapsulated polyaniline particles with melamine–formaldehyde resins

Polyaniline particles with low pH cannot be directly used in the electrorheological (ER) systems, since their emerald base form has a conductivity that is too high. Therefore, the pH of the polyaniline has been controlled to yield a lower conductivity. To improve the particle preparation method for polyaniline, which generates ER fluids with its semi-conducting characteristics, we synthesized microencapsulated polyaniline particles with melamine–formaldehyde (MF) resins. Microcapsules, containing polyaniline with a low pH as the core material, were prepared by polymerization of MF resin, which play the role of an insulator between the polyaniline particles. From rheological measurements, the yield stress of the ER fluid decreased with the increase of MF resin, and this effect enhanced as the applied electric field strength increased.