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STUDY OF THERMAL AND CHEMICAL STABILITY OF AMORPHOUS AROMATIC POLYMERS ?? SUPPORTS FOR PALLADIUM CATALYSTS

Linda Nikoshvili, Elena Bakhvalova, Valentina Matveeva

Abstract

Amorphous aromatic polymers synthesized by the knitting method are promising supports in catalysis, since they have high porosity (up to about 1000 m2/g) and can be synthesized by the simple one-step procedure using a variety of available aromatic monomers [1-4]. In catalysis, the stability of active phase is typically discussed, while the stability of polymeric support remains outside the scope. At the same time, many reactions require high temperature or application of strong acids or bases. In this work, a series of amorphous aromatic polymers was synthesized by the Friedel-Crafts reaction using FeCl3 as a polymerization catalyst and methylal as a crosslinking agent. Thermal stability of the polymers was studied by the TGA. Chemical stability was investigated in alkaline medium; the latter is necessary for such Pd-catalyzed reaction, as Suzuki cross-coupling. It was found that the polymers synthesized using N-heterocyclic monomers, especially the indole, can be unstable in the presence of a strong base – NaOH (confirmed by the DRIFTS and liquid nitrogen physisorption). Despite the disadvantage of the indole-derived polymer, this problem can be partially overcome by using a softer base, such as Na2CO3, which is also beneficial for the Suzuki reaction. At the same time, carbazole-derived polymers exhibited high stability. Moreover, the partial replacement of indole with such monomers as phenanthrene or 1-naphthol allowed for corresponding increase of polymer’ stability.

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