Fluorene-based linkers

Several fluorene-based linkers have been developed (Figure 15.13). In the 1980s, 9-(hydroxymethyl)fluorene-4-carboxylic acid was introduced for the synthesis of... 

Two copolymers were synthesized with different ratios of the fluorene-based monomer and the fluorenylidene linker. Both polymers were obtained in high yields and high molecular weight with Mw = 55,000-89,500 Da and exhibited excellent thermal stability. Glass transition temperatures ranged from 153 °C to 197 °C with decomposition temperature (5% weight loss measurend by TGA analysis) of 440 to 450 °C. 

The monomeric subunits in 50, esters of 2,5,7-trinitrodicyanomethylene-fluorene-4-carboxylate, has previously been used to create complexes with TTE-C4P 42 [91]. This led to the consideration that ditopic systems, such as 50, that incorporates an adequate glycol-linker between the two moieties would promote the formation of supramolecular oligomers when exposed to 42. Initial evidence of a supramolecular oligomer formation came from H NMR spectroscopic studies (cf. Eig. 12.38a). As expected based on the previous studies described above, the proton resonances of the aromatic TNDCE moiety 50 were shifted upheld, while the NH proton resonances of 42 were shifted to lower held. 

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