Morphology and structure of phenothiazine oligomers: Synthesis and effects of oxidants

Abstract

© 2019 Author(s). Phenothiazine oligomers were synthesized by oxidative oligomerization. Optimal reaction conditions were found: phenothiazine reacts with ammonium persulfate and silver (I), nickel (II), copper (II), and iron (III) nitrates in mechanochemical conditions in a mixture with p-toluenesulfonic acid. Effect of oxidants on the structure and morphology of oligomers was demonstrated by complex of physical methods, most prominent structural difference is demonstrated by MALDI mass-spectrometry and method of scanning electron microscopy. The use of metal nitrates leads to formation of oxidized oligophenothiazines (mass peaks correspond to side reactions leading to hydroxyl groups) which form bulk, granular material, the use of ammonium persulfate leads to formation of mesoporous material. Dielectric permittivity of oxidized oligomers is 2.9 - 10.2 in the case of metal nitrates while the maximum of permittivity was obtained for nanostructured oligophenothiazine - 4027.3 which was synthesized with ammonium persulfate as an oxidizing agent. We conclude that side reactions affect the morphology and dielectric permittivity - i.e. hydroxyl, quinone groups participate in forming intermolecular hydrogen bonds while in oligophenothiazine these interactions are less significant, which leads to mesoporous structure.