INSITU X-RAY-SCATTERING STUDY OF ANISOTROPIC SOLUTIONS OF HYDROXYPROPYLCELLULOSE SUBJECTED TO SHEAR-FLOW

Molecular orientation parameter values measured by laboratory-based X-ray scattering techniques are reported for liquid crystalline solutions of hydroxypropylcellulose in water subjected to a range of steady shear rates. The global orientation exhibits a marked transition from a low orientation at low shear rates to high values approximately 0.5 at higher shear rates. This transition occurs at shear rates in the range of 0.3-1 s-1 and correlates quantitatively with similar transitions observed using small-angle light scattering. This behaviour is attributed to an out-of-shearing plane to an in-shearing plane transition which has been predicted theoretically by Larson and Ottinger.