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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 1 $$S = \frac{1}{2}\left\langle {\left( {3{{\cos }^2}\theta - 1} \right)} \right\rangle $$ 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.
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 1 $$S = \frac{1}{2}\left\langle {\left( {3{{\cos }^2}\theta - 1} \right)} \right\rangle $$ 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.
Spinning from Lyotropic and Thermotropic Liquid Crystalline Systems
Ciferri, A. (author)
Developments in Oriented Polymers—2 ; 79-113
1987-01-01
35 pages
Article/Chapter (Book)
Electronic Resource
English
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