Electroactive materials have gained increasing attention for their intelligent applications. In this work, we report the design and synthesis of a novel electrochromic and electrofluorochromic dual-switching polyurea bearing oligoaniline and fluorescent triphenylamine units (PUOT). Cyclic voltammogram of PUOT exhibits two reversible redox couples at 0.96 V/0.73 V and 1.36 V/1.11 V (vs. Ag/AgCl reference electrode), ascribed to the redox transformation of oligoaniline and triphenylamine groups, respectively. In this wide potential window (0–1.6 V), the PUOT film reveals a unique multistage regulated electrochromic behavior with maximal transmittance contrast value of 38% switching from 0.0 V to 1.0 V, and partial transmittance contrast value of 14% (0–1.6 V) and 24% (1.0–1.6 V). Furthermore, its electrofluorochromic behavior has also been disclosed at the potential range of 0–1.0 V, which demonstrates that the oligoaniline groups should be served as electroactive units in this electrofluorochromic system. Our research not only presents a deep understanding of the optical-electrical modulation mechanism but also paves the way for their future applications.
Much attention has been paid to develop polymer-based composites utilized in electronic devices in the last two decades. This work introduces a high permittivity percolative composite material, fabricated by grafting the oligoaniline (OANI) onto the chains of acrylic resin elastomer (AE) through oxidative coupling polymerization (referred to the resulting nanocomposites as AE- g -OANI). The OANI is chosen as the filler because it combines the advantages of polyaniline (PANI) and good solubility. The composite films with different contents of OANI were prepared by the solution casting method and the physical blending PANI/AE composite films were also prepared for a comparison. The results show that the permittivity of AE-g-OANI is significantly improved compared to the pure AE, i.e. the dielectric constants of AE-g-OANI are 227 and 168 at 10 2 and 10 3 Hz, respectively, approximately 64 and 48 times of AE (3.5), as the volume fractions of OANI get close to the percolation threshold ( f c = 8.75). Meanwhile, the dielectric loss of AE-g-OANI composite (0.38 and 0.21 at 10 2 and 10 3 Hz) is much less than that of the PANI/AE composite (1.57 and 0.95 at 10 2 and 10 3 Hz) near the percolation threshold. We demonstrate that the origin of the obtained AE-g-OANI composite with high permittivity and low dielectric loss is closely relevant to the well dispersion of OANI particles, which creates more microcapacitors and enhances the MWS effect. In addition, the elongation at break and elastic modulus of AE-g-OANI composite near the percolation threshold are 820% and 5.3 MPa, respectively, at room temperature.
Yingchao Zhang,Yunfei Xie,Mingjuan Zhou,Erik B. Berda,Danming Chao
The elegant electroswitchable color/emission properties of electrochromic/electrofluorochromic dual-functional materials motivates the exploration of their new applications. In this work, a new poly (urea-urethane) was synthesized via nucleophilic copolymerization of electroactive oligoaniline derivative, solid-emissive tetraphenylethylene groups, and alkyl isocyanate. The resultant poly (urea-urethane) exhibited good electroactivity and desirable aggregation-induced emission properties. High-performance electrochromic/electrofluorochromic behavior had been disclosed with a high optical contrast ratio of ΔT = 50.4%, a moderate fluorescence on/off ratio of 10.5, and high coloration efficiency of 503 cm 2 /C at 768 nm. A reflective/emissive dual-mode display device had also been manufactured based on the resultant poly (urea-urethane) and charge-balancing V 2 O 5 , exhibiting a reversible color change and tunable fluorescence conversion upon the electric stimulus. Furthermore, this polymer showed an interesting color/fluorescence response to H 2 O 2 , due to the linkage mechanism between its redox states and optical properties . The spray-coated poly (urea-urethane) test strips were employed in visualized dual-determination of H 2 O 2 with gradual color change from gray to dark green, along with an obvious fluorescence change from light blue to dark, which displays easy operation and rapid detection.
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