Theories of Liquid Crystalline Polymers

The purpose of this chapter is to explain theoretically the formation of liquid crystal phases in polymer systems and to provide the basic concepts for designing and synthesizing liquid crystalline polymers. Liquid crystalline polymers combine features of both polymers and liquid crystals, thus we discuss the materials from two sides liquid crystallinity and polymer properties. Theoretical descriptions have encountered many difficulties in the past. One is that the present theoretical understanding of neither polymers or liquid crystals is complete. 

Rigid polymers are not the only class of polymers which can show liquid crystal phases. These phases are also found in the melts of polymers in which mesogenic units are incorporated in the backbone (main chain polymers) or attached as pendants to the backbone (side chain polymers). These liquid crystalline polymers will be discussed in later sections. 

Three main kinds of liquid crystal states nematic, cholesteric and smectic can occur in polymer systems. However, we will restrict the discussion to nematic polymers below, since it may be too early to adequately elaborate on the other two phases. 

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In a first step towards a comparable theory of liquid crystalline polymers, we study the effect of inherent chain flexibility with a Maier-Saupe theory. 

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