Orientational behaviour of thermotropic and lyotropic liquid crystal polymer systems under shear flow
Polymer Science Centre, JJ Thomson Physical Laboratory, University of Reading, Whiteknights, Reading, RG6 6AF, UK
Accepted: 17 June 1998
A comparison is made of the development of global orientation during shearing of lyotropic solutions of hydroxypropylcellulose with that observed for the thermotropic phase of hydroxypropylcellulose. At shear rates the behaviour of the two systems is similar, both during steady-state shear, and in terms of relaxation following cessation of shear flow. At low shear rates, the levels of orientation observed for the thermotropic system are substantially greater than observed for the lyotropic solutions. The relationship of these differences to variations in molecular parameters, viscous stress and to director tumbling is discussed.
PACS: 61.41.+e – Polymers, elastomers, and plastics / 83.50.Ax – Steady shear flows / 61.30.Gd – Orientational order of liquid crystals; electric and magnetic field effects on order
© EDP Sciences, 1998