Hybrid π-conjugated polymers from dibenzo pentacyclic centers: precursor design, electrosynthesis and electrochromics

pi-Conjugated polymers (CPs) represent one of the quite important and rapidly growing branches of flexible electrochromic materials. Electrosynthesized hybrid CPs employing dibenzo pentacycles (fluorenes, carbazoles, dibenzothiophenes, and dibenzofuran) as the backbones have received considerable attention owing to their special structures and interesting electrochromic performances. Recent studies show that polymers from these structures exhibit decent contrast ratios, favorable coloration efficiencies, low switching voltages, fast response time, excellent stability, and color persistence. Intrinsically, their electrochromic properties significantly depend on fine-tailoring of precursor monomer structures, and polymerization techniques and conditions. This review devotes to showing a clear picture of the research progress of dibenzo pentacycle-centered CPs via electrochemical polymerization, including fluorenes, carbazoles, dibenzothiophenes, and dibenzofuran-based hybrid electrochromic polymers. Critical influences of the tailored precursor structures on their electropolymerization and resultant polymer performances are highlighted, aiming at providing an insight for the development of novel fused ring-based polymer electrochromic materials.