Enhancement of electrochromic contrast by tethering conjugated polymer chains onto polyhedral oligomeric silsesquioxane nanocages

Copolymerization of aniline with octa(aminophenyl) silsesquioxane (OAPS) was performed, which resulted in polyaniline-tethered, polyhedral oligomeric silsesquioxane (POSS-PANI), with star-like molecular geometry. The spectro-electrochemical studies show that the electrochromic contrast of POSS-PANI is much higher than that of polyaniline (PANI). The great improvement can be attributed to the more accessible doping sites and the facile ion movement during the redox switching, brought by the loose packing of the PANI chains. This was evidenced by a drastic increase in ionic conductivity, a decrease in the electrical conductivity, and a decrease in the crystallinity and crystal size, with the increase of the OAPS concentration in the POSS-PANI.