Thermotropic SCLCP

Thermotropic side chain liquid crystalline polymers, SCLCPs... 

Liquid crystallinity can be attained in polymers of various polymer architectures, allowing the chemist to combine properties of macromolecules with the anisotropic properties of LC-phases. Mesogenic imits can be introduced into a polymer chain in different ways, as outhned in Fig. 1. For thermotropic LC systems, the LC-active units can be connected directly to each other in a condensation-type polymer to form the main chain ( main chain liquid crystalline polymers , MCLCPs) or they can be attached to the main chain as side chains ( side chain liquid crystalline polymers , SCLCPs). Calamitic (rod-Uke) as well as discotic mesogens have successfully been incorporated into polymers. Lyotropic LC-systems can also be formed by macromolecides. Amphiphihc block copolymers show this behavior when they have well-defined block structures with narrow molecular weight distributions. 

All the examples cited so far involve the formation of side chains by ionic com-plexation. Sallenave and Bazuin studied the selectivity of hydrogen-bond complex-ation in the presence of both ionic moieties and highly polar groups and also investigated the effect of these potentially interacting functions on the thermotropic behavior of SCLCP complexes [28]. A scheme of the compounds studied by these authors is 45 ... 

The elementary synthetic and structural principles of SCLCPs are now being elucidated using living polymerizations in which the effect of a single structural feature can be isolated, while other structural variables remain constant. In particular, living polymerizations are used to determine the molecular weight at which the thermotropic be-... 

If the mesogen and the length of the spacer are the primary factors determining the specific mesophase(s) exhibited by a given SCLCP, then its thermotropic behavior should be predictable by comparison to an appropriate model compound. Three possibilities for an appropriate model compound are shown in Table 6 and Fig. 12 using poly n-[(4 -(4"-cyanophenyl)phenoxy)-... 

In order to determine whether or not the alkyl substituent is necessary for low molar mass liquid crystals to mimic the thermotropic behavior of laterally attached SCLCPs, both l,4-bis[(3 -fluoro-4 -n-alk-oxyphenyl)ethynyl]benzenes [193, 196]... 

Increasing the spacer length has much the same effect on the thermotropic behavior of SCLCPs as increasing the length of the flexible substituent has on that of low molar mass liquid crystals. That is, it destabilizes some phases and stabilizes others. For example, just as increasing the length of the flexible substituent depresses the melting... 

Polymeric liquid crystals can be classified into either of two types, thermotropic and lyotropic, according to their formation conditions, or three types, main-chain, side-chain and complex liquid crystalline polymer (MCLCP, SCLCP and CLCP,... 

Other Factors Controlling the Thermotropic Behavior of SCLCPs as Studied... 

Traditionally, two major classes of thermotropic liquid crystalline polymers have been identified the so called main chain (longitudinal) and side chain (comb) types (MCLCPs and SCLCPs, respectively) (Fig. 2.5). More recently other variants have appeared these are combined LCPs which are hybrid between MCLCPs and SCLCPs, and the rigid rod types described by Watanabe et A great wealth of literature already exists in the form of unified texts and reviews which detail both the major classes of LCPs. Bibliographic data have been compiled" and reviews more or less specific to main chain or comb " polymer systems have appeared. We shall be concerned here only with main chain and side chain LCPs. 

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