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Electrorheological, Viscoelastic, and Creep-Recovery Behaviors of Covalently Bonded Nanocube-TiO2/Poly(3-octylthiophene) Colloidal Dispersions

2018    Sever, Evrim; Unal, Halil Ibrahim

In this study, nanocube-TiO2 and covalently bonded nanocube-TiO2/poly(3-octylthiophene), (P3OT) core/shell structured hybrid nano materials were dispersed in silicone oil (SO) and antisedimentation stabilities of these suspended particles were determined to be 31% and 65%, respectively. Polarizabilities (Delta epsilon(nanocube-TiO2) = 0.1925 and Delta epsilon(nanocube-TiO2/P3OT) = 0.0920) and relaxation times (lambda(nanocube-TiO2) = 3.4 x 10(-4) s and lambda(nanocube-TiO2/P3OT) = 2.7 x 10(-4) s) of dispersions were determined by dielectric measurements. Optical microscopy studies showed that these suspensions were highly polarizable under externally applied electric field strengths and classified as electrorheological (ER) active materials. The effects of volume fraction of dispersed phase, shear rate, shear stress, external electrical field strength, frequency, and temperature onto ER activities of these suspensions were studied. Yield stresses of nanocube-TiO2 and nanocube-TiO2/P3OT were determined to be 128 and 310 Pa, respectively. Viscoelastic studies revealed that the elastic characters of the particles were dominant to their viscous ones and elasticity moduli were determined to be 31.5 and 142 kPa, for nanocube-TiO2 and nanocube-TiO2/P3OT, respectively. Finally, the creep-recovery behaviors of these suspensions were identified and %recoveries of nanocube-TiO2/SO and nanocube-TiO2/P3OT/SO systems were determined to be 39% and 73%, respectively under tau = 5 Pa external shear stress. Because of the high polarizabilitiy, ER activity, vibration damping, and creep-recovery properties, the nanocube-TiO2/P3OT/SO suspension system was classified as smart material and suitable for potential vibration damping applications. (C) 2016 Society of Plastics Engineers