Thermotropic liquid-crystal polymers for high-performance character. These liquid-crystalline polymers simplify the applications are typically based on wholly aromatic polyester achievement of the high degree of molecular orientation necand polyamide architectures. The linear character of the aroessary in the solid state to approach theoretical tensile propmatic monomers produces polymer chains with stiff, extended erties. Figure 1 compares the fiber-forming process for conconformations. As a result, the chains organize themselves into ventional semicrystalline and nematic liquid-crystalline a nematic melt and readily orient in response to processing polymers and the resulting solid-state microstructures. flow fields. The close coupling between chain orientation and flow fields produces both a rich variety of materials and a high degree of controllability of their structure and properties (such as the tensile strength, elastic modulus and coefficient of thermal expansion). In this paper, we describe synthetic efforts to develop liquid-crystal polymer structures and the relationships between chain molecular structure, processing, and properties of this class of polymers in two distinct processing situations: Injection molding and fiber formation. The special importance of the orientational flow field in developing high orientation and excellent mechanical properties will be highlighted.

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