Polymer Electrolyte And Electrochromic Materials Based On Hyperbranched Polyethers

Viologen, a N, N'-4, 4'-bipyridine salt, can be reversibly oxided and redued withobvious color change. Although it has the special electrochromic property, littlemolecular weight viologen is not thermally stabile, easily dissolving from the surfaceof electrode, and poor film forming. Hyperbranched polyethers are potentiallyimportant electrolyte material, because of the low glass transition temperature, thecharacteristic and amorphous structure. HB-PE functionalized with viologen willcombine the electrochromic property with easy processing and better thermalstability. In this work HB-PEs were synthesized from glycidol and thenfunctionalized with viologen. Electrolyte films were prepared by the UV curing ofthe functionalized HB-PE with LiClO₄. A three-layer electrochromic devise (ECD)on ITO glass was fabricated with the funtionalized HB-PE material. The main resultsare as follows:1. Amorphous HB-PE with T_g of-38.1℃was synthesized by SCROP of glycidol.The-OH groups at the HB-PE chain ends were converted into reactive functionalgroups.2. Polymer electrolytes were prepared by photocuring the reactive HB-PEcontaining LiClO₄. The ion conductivity of this polymer electrolytes withO/Li⁺=6 was about 1.6×10^-5s/cm at room temperature, The content of Li⁺ salt has great effect on ion conductivitiy. The preparation of polymer electrolyte film issimple and solvent-free.3. HB-PE functionalized with viologens was prepared. The first and second redoxelectric potential, (E₁) and (E₂), of the electrochromic film, were-0.363v and-0.740v, respectively, with excellent recycling stability. By electric redox, thecolor of the film became purple, while by photic redox it became blue.