Polymer composites containing dispersed VO2 of various polymorphs: Effects of polymer matrix on functional properties

VO2 (B), VO2 (A) and VO2 (M) polymorphs were obtained by energy efficient semi-industrial hydrothermal process. Synthesis of thermochromic VO2 (M) was performed in two steps and included thermal treatment in an inert atmosphere. The crystallographic peculiarities were observed by powder X-ray diffraction study. Scanning electron microscopy and specific surface area estimation showed the influence of recrystallization on the particles size and shape. The technique of VO2 surface modification with electrically conductive polymer (polyaniline) was developed and proved by infrared spectroscopy. The impact of the polymer on the composite properties was investigated in case of three different crystal phases of VO2 with different functionality. Vibrating-sample magnetometry, impedance spectroscopy, cyclic voltammetry and room condition modelling showed that polyaniline surface leads to competitive interactions but doesn't ruin optical switching abilities of VO2 (M). Polyethylene glycol as electrically nonconductive matrix demonstrated the difference in electrical conductivity between VO2 phases while conductive polyaniline eliminated them.