INDEX ultrasonic effect

Some unexpectedly complex liquid solid interactions have been detected and studied by ultrasonic impedance measurements (ultrasonic impedometry). Small amounts of water and alcohols have pronounced effects on the physical state of hydrophilic polymers specifically, the high frequency shear modulus and crystallinity index of a poly (vinyl alcohol) film increases with water content to a maximum before normal solution phenomena occur. These effects are attributed to the increased molecular order owing to water hydrogen bonded between polymer chains. The unusual effects of moisture on a novel poly(vinyl chloride)/plasticizer system and on hydrophilic polymers other than poly (vinyl alcohol) are also described. [Pg.162]

The order parameter fluctuations in the isotropic phase are a weak optical effect which is not directly significant in the thermal grating diffraction. Therefore, again there is no direct relation between the optical and ultrasonic relaxation. In the isotropic phase the refractive index change is due to density change Ap therefore rj a Ap. Nematic correlation in the isotropic phase will influence the relaxation time observed in the optical experiment. However the weak temperature dependence of r implies that this is not substantial. [Pg.211]