Introduction

Functional liquid crystalline polymers (LCPs) are finding applications in many new, and sometimes unexpected, areas. Main-chain polymers are being used as the active component in electroluminescent display devices, and may find uses as non-linear optical materials, while, on the other hand, side-chain polymers, which were originally envisaged as replacements for small molecules in liquid crystal displays, are finding commercial use as passive optical films with carefully tailored optical properties. Ferroelectric liquid crystals are being used as temperature and pressure sensors, and have great promise as non-linear optical materials, with all of the attendant applications in optical computing and signal processing that such a use would bring. In all of these fields, cross-linking by photopolymerisation has become an important technique for the fixing of microstructures, and has led to a marked expansion in the range of possible uses. Finally, the relatively new field of liquid crystalline elastomers (LCEs) is producing applications as diverse as tunable lasers and artificial muscles.

The potential uses of functional LCPs are now too numerous to mention in detail, and many genuine commercial applications are beginning to appear. This chapter will attempt to give a flavour of the current range of possibilities.

Liquid crystalline polymers as optoelectronic materials

Electro-activity in organics

The delocalisation of electrons which can occur in some organic molecules, especially those with aromatic rings or other unsaturated bonds, means that the electronic distribution can be significantly influenced by various types of applied field, whether this be external, as with an electric field, or internal, by virtue of the attachment of electron donating or withdrawing groups to the molecule.