Acoustically induced birefringence in polymer aqueous solutions: The case of polyvinyl alcohol

Transient and stationary ultrasonically induced birefringence traces of various relatively dilute poly-vinyl alcohol aqueous solutions were measured over a range 500–1400 kHz of ultrasonic frequencies and 0.02–0.13 W/cm 2 of acoustic field amplitudes. The intrinsic value of the stationary birefringence for all polymer solutions investigated in this study was found to be proportional to the solution mass concentration, the square root of the ultrasonic intensity and the frequency of the ultrasound in agreement with theoretical predictions. Systematic analysis of the transient birefringence signals caused by the applied ultrasonic field has been performed in order to evaluate the orientational relaxation times from the viewpoint of dynamics of polymer chain orientation and anisotropy changes in polarizability. The results are discussed in the context of recent experimental studies and theoretical predictions of the ultrasonically induced birefringence in terms of transport phenomena.