Solid state physics of thermotropic

SOLID STATE PHYSICS OF THERMOTROPIC POLYESTERS INTERNAL FRICTION OF MESOMORPHIC STRUCTURES... 

There is currently considerable interest in the solid state physics of thermotropic liquid crystalline (LC) polymers and much emphasis is placed on studies regarding the solid-solid transitions and the chain dynamics of these systems. Recently, evidence for the occurrence of supercooled mesomorphic structures in the glassy state of polymers quenched from the anisotropic melt has been presented. ... 

There are some materials that exhibit more than one transition in changing from the solid to the liquid state. The molecular ordering in these mesophases lies between that of a solid and that of an isotropic liquid. This kind of material is known as a liquid crystal. Liquid crystals show physical properties in both the solid and liquid states. There are two types of liquid crystal one is lyotropic, whose phase transition is caused by changing the concentration or pH value of the solution, and the other is thermotropic, whose phase transition occurs on changing the temperature. 

Liquid crystal polymers (LCP) are polymers that exhibit liquid crystal characteristics either in solution (lyotropic liquid crystal) or in the melt (thermotropic liquid crystal) [Ballauf, 1989 Finkelmann, 1987 Morgan et al., 1987]. We need to define the liquid crystal state before proceeding. Crystalline solids have three-dimensional, long-range ordering of molecules. The molecules are said to be ordered or oriented with respect to their centers of mass and their molecular axes. The physical properties (e.g., refractive index, electrical conductivity, coefficient of thermal expansion) of a wide variety of crystalline substances vary in different directions. Such substances are referred to as anisotropic substances. Substances that have the same properties in all directions are referred to as isotropic substances. For example, liquids that possess no long-range molecular order in any dimension are described as isotropic. 

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