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Thermotropic main-chain liquid-crystalline polymers (LCPs) composed of azobenzene or azoxybenzene mesogens and flexible spacers with and without a phenyl side group have been characterized by gel permeation chromatography, differential scanning calorimetry, and X-ray diffraction. The polymers exhibit smectic phases in the well-accessible temperature range from room temperature up to 160 °C. The morphology of thin films on a solid substrate was studied by X-ray reflectometry and scanning force microscopy (SFM). The smectic layers are mainly oriented parallel to the film surface. On the basis of X-ray reflectometry and SFM investigations, it is concluded that, at least in thin films, the polymer main chains are not extended like in the common model for main-chain LCPs, but almost regularly folded.

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Four new w-ferrocenylalkyl diethyl malonates with varying length of the alkyl group from 4 to 10 methylene units were incorporated via Ti(OiPr),-catalyzed copolymerization into smectic liquid crystalline main-chain polymers in contents of about 10 mol-%. As mesogenic unit 4,4'-bis(6-hydroxyhexyloxy)azoxybenzene was used as diol component and diethyl phenyl malonate as diester component. Polymer analogous oxidation of the ferrocene units leads to liquid crystalline ionomers, which also form smectic phases. The ferrocene containing polymers were investigated in the oxidized and non-oxidized state of the ferrocene unit. Differential scanning calorimetry (DSC) data show a shift towards higher phase transition temperatures after oxidation, which is in agreement with the behaviour of classical ionomers. Small angle X-ray scattering (SAXS) experiments show an excess scattering to small angles, which is a hint for dispersed particles in the polymer matrix (ionic clusters). In one polymer series the ferrocene content was varied. Increasing the ferrocene content changes the type of the LC phase from smectic A to nematic presumably because of the bulkiness of the neutral ferrocene group. It is, however, possible to restore the smectic A phase by an oxidation of the ferrocene units to ferrocenium ions. This is a result of microphase separation in ionic domains and non-ionic domains, which supports the formation of layered structures.

We have incorporated three new diethyl w-ferrocenylalkylmalonates into a smectic liquid crystalline main-chain polymer in contents of about 10 mol-%. As mesogenic unit 4,4'-bis(6-hydroxyhexyloxy)azoxybenzene was used as diol component and diethyl phenylmalonate as diacid component. Three ferrocene-containing polymers were investigated in the oxidized and non-oxidized state of the ferrocene unit varying the counterion. DSC data show a shift toward higher phase transition temperatures after oxidation, which increases with the length of the alkyl spacer between main chain and ferrocene unit. Xray measurements of the non-oxidized species show an unusual increase of the smectic layer thickness with increasing length of the alkyl spacer.