Liquid Crystal Spinning

Lyotropic liquid crystalline polymers can be sprm into fibers by using a wet or gel spinning process, while thermotropic Uqrrid crystalline polymers can be made into fibers by melt spinning. Although both lyotropic and thermotropic liquid crystalline polymers can be made into fibers, most successful liqrrid crystal fibers are based on lyotropic polymers. One such example is polyphertylene terephthalamide (PPTA, Kevlar ), which was first produced by DuPont in 1972. 

Figuiie 9.22. dscosity-concentration relationship of lyotropic Uquid crystal polymers. 

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Boerstoel H (2006) Self-organization phenomena in liquid crystal spinning, Sen i Gakkaishi 62 93-101. 

Chapter 2 focused on the evolution of a nuclear spin system without examining how it achieves thermal equilibrium with the lattice by energy exchange. The lattice consists of all degrees of freedom, except those of the nuclear spins, associated with molecular rotations and translations in physical systems such as liquid crystals. Spin-lattice relaxation describes how the system of nuclear spins evolves towards thermal equilibrium with the large heat reservoir, the lattice. The spin relaxation rates with which the nuclei arrive at their equilibrium magnetization may be experimentally determined. There is a well-defined connection between the relaxation rates and the dynamics of the lattice provided that the coupling interactions between the nuclear spin system and the lattice are known. Thus, nuclear spin relaxation may be used to study motional processes in molecular systems. 

Motivated by these criticisms, a unified hydrodynamics theory (hereafter referred to as UHT) of condensed matter [11-13] has been developed based on the theoretical framework of fundamental physical concept which is succinctly called the grand synthesis by Lubensky [14]. From its nature, the UHT is applicable to a wide range of hydrodynamics including various phases of liquid crystals, spin systems, even crystals, and so on. In the following, we briefly review the UHT of nematodynamics. 

What is liquid crystal spinning Describe the unique feamres of liquid crystal spinning. 

Freed J. H. Stochastic-molecular theory of spin-relaxation for liquid crystals, J. Chem. Phys. 66, 4183-99 (1977). 

The frustration effects are implicit in many physical systems, as different as spin glass magnets, adsorbed monomolecular films and liquid crystals [32, 54, 55], In the case of polar mesogens the dipolar frustrations may be modelled by a spin system on a triangular lattice (Fig, 5), The corresponding Hamiltonian consists of a two particle dipolar potential that has competing parallel dipole and antiparallel dipole interactions [321, The system is analyzed in terms of dimers and trimers of dipoles. When the dipolar forces between two of them cancel, the third dipole experiences no overall interaction. It is free to permeate out of the layer, thus frustrating smectic order. 

Courtieu, J., Bayle, J. P., Fung, B. M. Variable angle sample spinning NM R in liquid crystals. Prog. Nucl. Magn. Reson. Spectrosc. 1994, 26,141-169. 

Recent solid state NMR studies of liquid crystalline materials are surveyed. The review deals first with some background information in order to facilitate discussions on various NMR (13C, ll, 21 , I9F etc.) works to be followed. This includes the following spin Hamiltonians, spin relaxation theory, and a survey of recent solid state NMR methods (mainly 13C) for liquid crystals on the one hand, while on the other hand molecular ordering of mesogens and motional models for liquid crystals. NMR studies done since 1997 on both solutes and solvent molecules are discussed. For the latter, thermotropic and lyotropic liquid crystals are included with an emphasis on newly discovered liquid crystalline materials. For the solute studies, both small molecules and weakly ordered biomolecules are briefly surveyed. 

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