Synthesis and electrochromic performance of oligoaniline-containing polyureas capped with various functional groups

Tuning the molecular structure is an effective strategy to modulate the electrochromic behaviors of conducting polymers. In this contribution, a novel oligoaniline-containing polyurea ended with reactable isocyanate groups is designed and synthesized via nucleophilic polymerization. Then various functional groups such as o-toluidine, poly(ethylene glycol) (PEG), ethoxysilane, and congo red (CR) are introduced as end groups to modulate the electrochromic performance. Hydrophilic PEG could improve the switching speed due to the rapid electrolyte ions diffusion into polymer film through the hydrophilic region. An enhanced switching stability is afforded by crosslinkable ethoxysilane end groups, ascribed to crosslinked densified surface and great adhesion force between the electrochromic layer and ITO substrate through the hydrolysis reaction. Moreover, an ample color change is achieved by introducing colored CR as end groups.