Spinning from Lyotropic and Thermotropic Liquid Crystalline Systems

Abstract

Amorphous orientation with conventional flexible polymers is hindered by the natural tendency to recoil of the molecules, by the lack of a microscopic degree of order, and the occurrence of chain entanglement. Rigid polymers in a nematic mesophase should be more simply oriented than flexible ones since they have no tendency to recoil and exhibit a microscopic order of molecules described by the so-called order parameter. In fact, in order to fully orient the rigid nematic polymers, it is necessary to

• (1) increase the order parameter:¹

  $$S = \frac{1}{2}\left\langle {\left( {3{{\cos }^2}\theta - 1} \right)} \right\rangle $$

  (1)

  where θ is the average angle between the molecular axis and the director (a vector representing the average molecular orientation at any point of the liquid¹) toward the value S=1 expected for complete orientation;

• (2) orient the director along the flow direction or, according to an alternative (less precise¹) description, to transform the ‘polydomain’ texture (rich in disinclinations) into a ‘monodomain’ texture.² The overall process is schematized in Fig. 1.