LIQUID-CRYSTALLINE AND RIGID-ROD NETWORKS

Starting about a decade ago, researchers began to explore the use of LC networks as a means of coupling mechanical forces to the mesomorphic character of networks. In so doing, the field of LC elastomers was created and the resulting ferroelectric and piezoelectric materials are beginning to revolutionize the field of polymers. More recently, industry has begun to investigate rigid-rod and LC thermosets as a means of introducing the desirable physical properties of LC thermoplastics in thermoset systems. These polymer networks offer such capabilities as tuned coefficients of thermal expansion and increased fracture toughness. Finally, efforts are being made to develop networks which while not necessarily mesomorphic, do have highly oriented structures to produce networks with NLO properties. Long-term orientational stability is one of the features offered by these new materials. This review will examine all three types of networks, with the major focus being on LC thermosets.