Electrochromic conjugated polymers employed tetraphenylethylene building block with moderate optical contrast and fast response time

Abstract

Tetraphenylethylene (TPE) can improve nature-state transmittance and response time when used as a building block in electrochromism. Two precursors of TPE-based molecules (TPE‐2T and TPE-2E) were successfully synthesized by Stille coupling reaction, and electropolymerized to yield the corresponding polymers of P(TPE‐2T) and P(TPE-2E). Characterizations of the above polymers were performed by cyclic voltammetry (CV), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Furthermore, the spectroelectrochemistry and electrochromic properties of P(TPE‐2T) and P(TPE-2E) were compared investigated. P(TPE‐2T) demonstrated yellow in the neutral state to deep green in the oxidized state while P(TPE-2E) showed colorless-to-violet color changes with 0–1.4 V. P(TPE‐2T) displayed much better electrochromic performance due to its electroactivity with moderate optical contrast (32%) and fast response time (0.9 s). However, P(TPE-2E) showed low optical contrast, which is in agreement with the spectroelectrochemistry result (only slight wavelength shift between the neutral state and the oxidized state). From these results, P(TPE‐2T) can be further explored electrochromic material towards indoor electrochromic product and flexible display.