Electrofluorochromism has attracted great attention due to the intelligence optoelectronic and sensing applications. The intrinsically switchable fluorophores with high solid-state fluorescence are regarded as key for ideal electrofluorochromic materials. Here, we reported an AIE-active polyamide with diphenylamine and tetraphenylethylene units, showing high fluorescence quantum yield up to 69.1% for the solid polymer film and stable electrochemical cycling stability. The polyamide exhibited reversible color and emission switching even in hundreds of cycles, and the fluorescence on/off contrast ratio was determined up to 417, which is the highest value to our knowledge. Furthermore, as the response time is vital for the real-life applications, to speed up the response of electrofluorochromism, a porous polymer film was readily prepared through a facile method, notably exhibiting high fluorescence contrast, long-term stability and obviously improved response, due to the sharply increased surface area. Therefore, the AIE-functionalization combining the porous structure strategy will synergistically and dramatically improve the electrofluorochromic performance, which will also promote their practical applications in the near future.

Aiming to develop soluble and colorless polyimides, two novel diamines, 2,5-bis(2-trifluoromethyl-4-aminophenoxy)-1,4:3,6-dianhydrosorbitol (2a) and 2,5-bis(2-methyl-4amino-phenoxy)-1,4:3,6-dianhydrosorbitol (2b), were designed and synthesized by the reduction of corresponding dinitro monomer which was obtained via solvent-free melt heating method. Polyimides (PI-(1-5)) containing 1,4:3,6-dianhydro-Dglucidol fragments were prepared from 2a and five kinds of common dianhydrides and PI-6 was synthesized from 2b and 4,4 0 -(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) via a two-step thermal imidization. All the polyimides were readily soluble in common polar solvents and could afford flexible, tough, and transparent films with transparency as high as 87% at 450 nm. Meanwhile, PI-(1-6) exhibited unexpectedly low dielectric constants of 2.02-2.52 at 1 MHz. In addition, analogs PI-7 derived from 2,5-bis(4-amino-phenoxy)-1,4:3,6-dianhydrosorbitol (2c) and 6FDA and PI-8 derived from 4,4 0 -bis(4-amino-2-trifluoromethylphenoxy)biphenyl (2d) and 6FDA were also obtained via a two-step thermal imidization for comparision with PI-(1-6) on aspects of thermal, mechnical, optical, electrical, and morphological properties. The structure-property relationships of PI-(1-8) were discussed in detail.

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A series of novel benzimidazole-containing aromatic polyimides were prepared from synthesized 5,4 0 -diamino-2-phenyl benzimidazole (DAPBI), and commercial dianhydrides by the conventional two-step polymerization. The obtained films were amorphous and could afford flexible, transparent, and tough films with excellent thermal and mechanical properties. They showed high levels of tension strength of up to 234 MPa, modulus of up to 5.6 GPa without any stretching. According to thermal stability measurements, the glass-transition temperatures of the polymers were observed between 329 and 425 C. The 5% weight-loss temperatures of most polyimides were above 600 C in nitrogen. Excellent properties of these polyimides were proved to be attributed to the rigid-rod structure and hydrogen bond of intermacromolecular. SAXS and SEM results showed self-molecular orientation caused the formation of rod-like extended conformations. It was demonstrated that high degree of supramolecular order led to the increase of thermal stability and mechanical properties of the polyimide films.

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