Electrokinetic, electrorheological and viscoelastic properties of Polythiophene-graft-Chitosan copolymer particles

Abstract

Electrokinetic properties of Polythiophene-graft-Chitosan (PT-g-CS) copolymer were investigated by means of zeta (ζ)-potential measurements as a function of pH, electrolytes, surfactants, and temperature in aqueous medium. The ζ-Potential of pure PT was observed to enhance from +25mV to +36mV after grating with polycationic CS. Concomitantly, the isoelectric point of the pure PT shifted from 6.4 to 8.3. The ζ-Potential of PT-g-CS dispersion also shifted to more positive regions with increasing valency of the electrolytes and concentrations of cationic surfactant (cetyltrimethylammonium bromide). The ζ-Potential of PT-g-CS was determined to be +38mV which indicated colloidal stability in silicone oil (SO) medium. Electrorheological (ER) and viscoelastic measurements revealed that the PT-g-CS/SO system has elasto-viscous behavior under applied electric field strengths. The yield stress of the ER fluid was determined to be a function of the electric field strength in a power law form as τy=E1.55 which obey to the conduction model. Creep and creep-recovery tests revealed reversible non-linear viscoelastic deformations of %31<%40<%43 under E=1; 2 and 3kV/mm conditions.