Wideband measurement of shear induced birefringence by quadrupole method

Abstract

We developed a new method for the measurement of the dynamic birefringence induced by the alternating shear deformation in fluid samples. A quadrupole piezoactuator generates the pure shear deformation in the frequency range from 1 Hz to 5 kHz and causes the molecular orientation, or the anisotropic conformation of polymers and molecular associations, which is observed by the optical ellipsometry technique. The spectrum of the shear-induced birefringence observed for the isotropic phase of the liquid crystal p-n -hexyl p′ -cyanobiphenyl (6CB) shows linear dependence on the frequency up to 5 kHz, corroborating the effective band of the experimental system. The sensitivity of the system was demonstrated by the quantitative measurement of the birefringence for the isotropic phase of p-n -pentyl p′ -cyanobiphenyl (5CB). The system was also applied to the aqueous solution of the worm such as micelles and the result shows the relaxation of shear induced birefringence at around 10 Hz, which agrees well with the previous reports. © 2006 American Institute of Physics.