Thermotropic Liquid-Crystalline Aliphatic Polyimides

Recently much effort has been made to induce liquid crystallinity in polyimides. Kricheldorf et al., Chen et al., and Sato et al. have suggested that an aromatic im-ide ring may be an excellent mesogen through their studies on thermotropic liquid-crystalline polyimide-esters [41-54] and polyimide-carbonates [55, 56]. Some thermotropic properties of aromatic polyether-imides have also been reported by Asanuma et al. [57]. 

More recently, we have found that the terphenyltetracarboxylic acid-based polyimides P-XTP showed thermotropic liquid-crystalline phase [21,22]. As far as we know, this is the first example of the simple polyimides showing thermotropic liquid crystallinity. 

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Keywords Liquid-crystalline polyimides, Poly(ester-imide)s, Thermotropic, Nematic, Smectic, Cholesteric, Mesogen, Layer structure, Aliphatic spacer, Trimellitimide... 

By far the largest group of liquid crystalline polymers containing imide groups are copoly(esterimide)s (PEIs). These have been sub-divided into flexible copolymers containing aliphatic spacers and wholly aromatic copolymers. There are several reports of copoly(amide-imide)s and copoly(ether-imide)s (both thermotropic and lyotropic) and these are treated separately. There are only a few examples of wholly aromatic imide containing LCPs, as polyimides frequently melt well above their decomposition temperature. Successful attempts have been made to incorporate flexible spacers, but in most instances the spacers are based on ether units, and the polymer is more strictly classified as a poly(etherimide). 

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