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Silicon- or Carbon-Cored Multifunctional Carbazolyl Monomers for the Electrochemical Generation of Microporous Polymer Films

Abstract:

A series of four tetra- or octacarbazolyl-substituted, tetraphenylmethane/-silane monomers have been oxidatively coupled into microporous polymer networks (MPNs). Chemical polymerization with iron(III) chloride gives bulk MPNs with BET surface areas (SBET) of up to 1331 m2 g-1 (for the octacarbazolyl-substituted tetraphenylmethane monomer). Slightly increased SBET values result for the materials made from the octacarbazolyl monomers if compared to the tetracarbazolyl analogues, while the exchange of the central carbon by a silicon atom leads to decreased surface areas. The latter phenomenon might be related to electronic interactions of aromatic substituents through the silicon centers. This may cause a reduced reactivity of the carbazoles after the initial oxidative couplings and finally a reduced cross-linking density of the resulting MPNs. Moreover, electrochemical oxidative coupling enables the formation of thin polymer films on the working electrode. These films also show high SBET values that are only slightly reduced if compared to the corresponding bulk MPNs. Electrochemical quartz microbalance measurements allow for an in-situ characterization of the electrochemical MPN generation. Finally, the electrochemical reduction of a series of nitroaromatic compounds (NACs) on MPN-modified glassy carbon electrodes is studied and applied for high sensitivity NACs detection up to the ppb range.