Orientation Dynamics of Main-Chain Liquid Crystal Polymers. 2. Structure and Kinetics in a Magnetic Field

Several aspects of molecular organization and dynamics in liquid crystal polymers have been revealed by orientation kinetics in a magnetic field. The technique used was pulsed broad-line proton NMR, and the polymers were liquid crystal copolymers synthesized in our laboratory. Interestingly, isothermal aging before application of the magnetic field leads to a drastic reduction in orientation time, reflecting the nonequilibrium nature of the mesophase structure. The fitting of data to a theoretical model of the orientation process plus other observations leads to the following conclusions. The liquid crystal fluid either is multiphasic or contains an interphase region in which chain segments have greater mobility and perhaps less order. At least for samples in nonequilibrium states, experimental results could be consistent with segments of a single chain traversing various orientationally ordered domains. This type of molecular organization may be viewed as a liquid fringed micelle.