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Electrochromic devices based on high-performance polymer materials with exceptional optical contrast, superior cycling stability, and large coloration efficiency are critical for the advancement of electrochromics, and have the potential to innovate a broad range of applications, including flexible displays and wearable electronics. Here, we design and synthesize three precursors of fluorobenzene-3-methylthiophene D-A-D type polymers through one-step Stille coupling, and then prepare the corresponding polymer films with good electrochemical and electrochromic properties via low-potential electropolymerization at 0.52 V vs Ag/AgCl. Interestingly, such polymers exhibit overall high electrochromic performances during the electrochemical reaction with inversible color changes between yellow and dark blue, including high optical contrast (83% at 1050 nm), fast response time (1.4 s / 0.8 s), and long-term stability (< 2% reduction after 250 cycles). As-fabricated electrochromic devices display excellent cycling stability (< 3% optical contrast degradation after 1,000 cycles) at a low drive voltage (0.8 V). Due to these excellent electrochromic properties, d -A-D type polymers based on fluorobenzene-3-methylthiophene can be further developed for practical applications such as near-infrared camouflage and E-displays. [Display omitted] [ABSTRACT FROM AUTHOR]

High polymerization degree is critical for polypyrene applying in fluorescent sensing field, which closely related to high sensitivity. However, polypyrene films reported are either insoluble and unprocessable or soluble with few repeat units. In this work, we synthesized a poly(1-pyrenebutyric acid) (PPBA) via electrochemical polymerization in boron fluoride ethyl ether system and the degree of polymerization was up to 43, which showed good fluorescence. The polymer showed high selectivity toward to Cr 2 O 7 2− among sixteen anions and twenty cations in ethyl alcohol system, and the limit of detection was as low as 1.58 fM. Transmission electron microscope results showed that the quenching mechanism of the PPBA was Cr 2 O 7 2−-induced inter- and intra-polymer aggregation of polymer chains in solution. Finally, PPBA was successfully applied in milk detection, implying that PPBA can realize the ultra-trace detection of Cr 2 O 7 2− in practical application. High degree of polymerization of poly(1-pyrenebutyric acid) fluorescence sensor that can specifically recognize Cr 2 O 7 2−. [Display omitted] • The fluorescence sensor PPBA with high polymerization degree was obtained by electropolymerization. • PPBA was highly sensitive to Cr 2 O 7 2− and the limit of detection was as low as 1.58 fM. • PPBA had a high anti-interference ability when sensing Cr 2 O 7 2−, avoiding the interference of common anions and cations. • PPBA was successfully used to detect Cr 2 O 7 2− in milk. [ABSTRACT FROM AUTHOR]