Mechanical and Thermophysical Properties of Polymer Liquid Crystals (Polymer Liquid Crystals Series, Number 3)

may never overcome the effects of hysteresis and stress (see Chapters 6 and 12). The first sentence of the reference work, Handbook of Liquid Crystals, reads: The terms liquid crystals, crystalline liquid, mesophase, and mesomorphous state are used synonymously to describe a state of aggregation that exhibits a molecular order in a size range similar to that of a crystal but acts more or less as a viscous liquid: [2] In other words, molecules within a liquid crystalline phase possess some orientational order and lack positional order; furthermore, the shape of a liquid crystalline sample is determined by the vessel in which it is contained rather than by the orientational order of its aggregated molecules. The authors recognized the limitations and imprecision of this definition but, like others preceding them, could not devise a simple and generally applicable one that is better. Regardless, the terms 'liquid crystal' and 'mesophase' should not be used interchangeably. As mentioned above, all liquid crystals are mesophases, but all mesophases are not liquid crystals. Recent studies, employing elaborate and sophisticated analytical techniques, have permitted finer distinctions between classical crystals and mesophases. At the same time, they have made definitions like that from the Handbook of Liquid Crystals somewhat obsolete for reasons other than terminology. One part of the problem arises from the use of a combination of bulk properties (like flow) and microscopic properties (like molecular ordering) within the same definition. Front Matter....Pages i-xiv Front Matter....Pages 1-1 Creation of liquid crystalline phases: a comparative view emphasizing structure and shape of monomer liquid crystals....Pages 3-40 Inorganic polymer liquid crystals....Pages 41-58 Design of polymer liquid crystals with non-covalent bonds....Pages 59-100 Morphology of Thermotropic Longitudinal Polymer Liquid Crystals....Pages 101-123 Polymer liquid crystals in solution....Pages 124-143 Front Matter....Pages 145-145 Memory effects in polymer liquid crystals: influence of thermal history of phase behavior....Pages 147-171 Longitudinal polymer liquid crystal + engineering polymer blends: miscibility and crystallization phenomena....Pages 172-213 Thermal expansivity....Pages 214-252 Front Matter....Pages 253-253 Phase diagrams of polymer liquid crystals and polymer liquid crystal blends: relation to mechanical properties....Pages 255-305 Development and relaxation of orientation in pure polymer liquid crystals and blends....Pages 306-341 Flow induced phenomena of lyotropic polymer liquid crystals: the negative normal force effect and bands perpendicular to shear....Pages 342-406 Creep and stress relaxation....Pages 407-430 Thermoreversible gelation of rigid rod-like and semirigid polymers....Pages 431-447 Elastic moduli of polymer liquid crystals....Pages 448-494 Computer simulations....Pages 495-510 Back Matter....Pages 511-520 A crystal may be defined microscopically as a condensed phase in which molecules possess both orientational and three-dimensional long-range order and are not able to change conformations; macroscopically, the shape of a crystal depends upon (microscopic) molecular positions within a lattice, but not upon the shape of the vessel in which it is held.