Shaowei Guan

Transmissive-to-black switching electrochromic (EC) polymers have attracted considerable attention toward the development of low-cost, low-energy-demand passive displays. However, most reported transmissive-to-black switching EC polymers have high applied potential and low cycling stability, which significantly restrict their practical application. To address this issue, we propose a new structure design concept from the perspective of molecular structural changes by systematically investigating three different types of tetraphenylethylene (TPE)-based π-bridges connected with a diphenylamine (DPA) electroactive unit (pendant-grouped, straight-chained, and hyperbranched). The structural changes of the TPE-based π-bridge during electrochemical redox and the EC performance of polyimides are studied. All the designed polyimides (PG-TPE-PI, ST-TPE-PI, and HB-TPE-PI) exhibit overall transmissive-to-black EC performance. In particular, PG-TPE-PI presents a high response speed (2.29 s/2.51 s), excellent open circuit stability (over 24 h/72 h), and high coloration efficiency (566 cm² C⁻¹), as well as first-class cycling stability for a transmissive-to-black polymer material (3000 cycles in an open system), thereby showing excellent application potential.

Organic materials have garnered intensive focus as a new group of electrodes for lithium-ion batteries (LIBs). However, many reported organic electrodes so far still exhibit unsatisfying cycling stability because of the dissolution in the electrolytes. Herein, a novel azo-linked hexaazatrianphthalene (HATN)-based polymer (AZO-HATN-AQ) is designed and fabricated by the polymerization of trinitrodiquinoxalino[2,3-a:2',3'-c]phenazine (HATNTN) and 2,6-diaminoanthraquinone (DAAQ). The abundant redox-active sites, extended π-conjugated planar conformation, and low energy gap endow the AZO-HATN-AQ electrode with high theoretical capacity, excellent solubility resistance, and fast Li-ion transport. In particular, the fully lithiated AZO-HATN-AQ still keeps the planar structure, contributing to the excellent cycling stability. As a result, AZO-HATN-AQ cathodes show high specific capacity (240 mAh g^-1 at 0.05 A g^-1), prominent rate capability (98 mAh g^-1 at 8 A g^-1), and outstanding cycling stability (120 mAh g^-1 after 2000 cycles at 4 A g^-1 with 85.7% capacity retention) simultaneously. This study demonstrates that rational structure design of the polymer electrodes is an effective approach to achieving excellent comprehensive electrochemical performance.

All-organic symmetric lithium-ion batteries (LIBs) show promising prospects in sustainable energy storage systems, due to their environmental friendliness, structural diversity and low cost. Nevertheless, it remains a great challenge to explore suitable electrode materials and achieve excellent battery performance for all-organic symmetric LIBs. Herein, a squaraine-anthraquinone polymer (PSQ) electrode material was designed through rational molecular engineering. The well-designed extended π-conjugated system, donor–acceptor structure, abundant redox-active sites and rational manipulation of weak inter-/intramolecular interactions endow the PSQ electrode with outstanding electrochemical performance. The capacity of the PSQ cathode can be optimized to 311.5 mA h g⁻¹ by in situ carbon-template polymerization. Impressively, PSQ-based all-organic symmetric LIBs displayed high reversible capacity (170.8 mA h g⁻¹ at 50 mA g⁻¹), excellent rate performance (64.9% capacity retention at 4000 mA g⁻¹vs. 50 mA g⁻¹), ultralong cycle life up to 30 000 cycles at 2000 mA g⁻¹ and 97% capacity retention after 2500 cycles at 500 mA g⁻¹, which is one of the best comprehensive battery performances among the all-organic LIBs reported thus far.

A novel hexaazatrinaphthylene-based (HATN) azo polymer (PAH) was synthesized from a newly designed tri-nitro compound trinitrodiquinoxalino[2,3-a:2',3'-c]phenazine (HATNTN) through a Zn-induced reductive homocoupling reaction and used as a cathode material for lithium-ion batteries (LIBs). The integration of redox-active HATN units and azo linkages can improve the specific capacity, rate performance, and cycling stability of the PAH cathode. The control LIBs were assembled from HATNTN, in which HATNTN can be electrochemically reduced to an HATN-based azo polymer. Compared with the HATNTN cathode, the PAH cathode delivers higher specific capacities with much-improved cycling stability (97 mA h g^-1 capacity retention after 1500 cycles at 500 mA g^-1, which is around 28 times that of the HATNTN cathode) and considerably better rate performance (118 mA h g^-1 at 2000 mA g^-1, which is around 90 times that of the HATNTN cathode), simultaneously. This work provides a chemical polymerization strategy to construct extended π-conjugated azo polymers with multiple redox centers from nitro compounds for developing high-performance LIBs.

In order to prepare a coating with better corrosion resistance, the double‐layer coatings are designed to work together in this article. The double‐layer coatings are made of polyethersulfone and epoxy resin as the matrix resin. Polyaniline (PANI) of different contents was added to the matrix resin by weight to form the primer coats, which was named as d‐0, d‐20, d‐40, d‐60. And polytetrafluoroethylene was introduced into the matrix resin to prepare the surface coats. A two‐layer coating was prepared by coating the surface layer on the primer layer, named as S‐0, S‐20, S‐40, S‐60. The surface morphology of the primer coatings and the cross section morphology of the two‐layer coatings were determined by field emission scanning electron microscopy. The anticorrosion property of the coatings was studied by water absorption, adhesion, salt spray corrosion acceleration test and electrochemical impedance test. The results indicate that the 40 wt% PANI composite coating shows the best corrosion resistance.

Two novel hyperbranched polyimides (HBPIs) bearing bis(trifluoromethyl)‐triphenylamine moiety were prepared by condensation polymerization of a triamine monomer, N,N‐bis[4‐amino‐2‐(trifluoromethyl)phenyl]‐1,4‐benzenediamine (ATPB), with oxydiphthalic dianhydride (ODPA) and hexafluoroisopropyl phthalic anhydride (6FDA). The trifluoromethyl group was introduced into HBPIs to improve the property of the memory device. The resulting hyperbranched polyimides exhibited high molecular weights (weight‐average molecular weights large to 7.51×10 ⁴ with a polydispersity of 1.63), outstanding organic‐solubility and excellent thermal stability (5 % thermal weight‐loss temperature up to 518 °C). Memory devices based on these hyperbranched polyimides showed similar rewritable nonvolatile memory characteristics but with different threshold voltages. The switching voltage was found to have a dependence on the energy barrier between polymer active layer and electrodes. These devices displayed favorable stability in both OFF and ON states with retention time long to 10 ⁴ s and ON/OFF current ratio as high as 10 ⁶ . The space charge‐limited conduction model and local filaments formation were responsible for the switching behaviors of these memory devices. The results indicate that these hyperbranched polyimides are promising candidates for polymer memory application.