Ferrocene-Containing Liquid Crystal Polymers

Polyesters 26 represent the first ferrocene-containing liquid crystal polymers [28]. These copolymers were found to be insoluble in THF, toluene, dichloromethane, chloroform, p-chlorophenol, and tetrachloroethane. The terephthaloyl chloride/iso-phthaloyl chloride ratio was maintained constant (7 3), but the content of the ferrocene unit was varied from 0 to 100%. 

Except for the structure containing 100% of ferrocene unit, which decomposed before melting, all the organometallic copolymers exhibited birefringent melts. Nematic textures were identified by means of polarized optical microscopy and, in one case, by X-ray diffraction studies. For comparison purposes, a polymer without ferrocene unit was prepared, but showed no mesomorphism. The authors deduced that the ferrocene framework was contributing to the liquid crystallinity of the ferrocene-containing polymers. 

After our investigations on low molar mass ferrocene derivatives, we examined the thermal properties of isomeric polymeric structures. 

Polycondensates 27 and 28 (Fig. 9-22), incorporating either the 1,3- or 1,1 -disubstituted ferrocene unit, were prepared by solution polymerisation. Polymers 27 [25] were obtained by reaction of the novel monomer 29 [25] (Fig. 9-23) with the desired bis(acid chloride) 31 (Fig. 9-23) in refluxing CH2CI2 in the presence of triethylamine. Polymers 28 [25] were prepared following the same procedure from bis-phenol 30 [16] (Fig. 9-23). 

Ferrocene-containing polymers 27 and 28 were soluble in dichloromethane and chloroform, and partly soluble in THF. Analysis by gel permeation chromatography (GPC) indicated molecular weights in the range 10000 — 20000, and revealed, therefore, an oligomeric nature for 27 and 28. 

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The section commences with monosubstituted ferrocene derivatives, after which the influence of the substitution pattern on the formation and stability of liquid-crystalline phases for disub-stituted ferrocene derivatives will be discussed. Next, the influence of the three-dimensional structure of ferrocene on the mesomorphic properties will be highlighted, optically active ferrocene materials will be described and, finally, ferrocene-containing liquid-crystalline dendrimers will be introduced ferrocene-containing liquid-crystalline polymers will not be reported. Note that a review devoted to ferrocene-containing thermotropic liquid crystals has already been published. ... 

It was also shown that it is possible to synthesize polymethacrylate liquid crystal polymers with mesomorphic properties that contain ferrocenes with two flexible chains at the 1,1 -positions [59]. Based on dilatometric measurements, a head-to-tail molecular arrangement of the monomeric units occurs within the smectic A phase. Because of special electrochemical properties of ferrocene, these materials are of interest for developing electroactive mesomorphic polymers. The structure of the polymer can be shown as follows [59] ... 

Micellar structures, J-aggregates, liquid crystals, i-gels, ferrocene-containing polymers and topospecific chemistry at surfaces and in single crystals, and... 

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