Synthesis And Performance Of Multicolor Electrochromic Materials Based On Oligoaniline Groups

Electrochromism refers to the phenomenon that the material can provide a stable and reversible changes in optical properties(transmittance,reflectance,absorption rate,etc.)under applied electric field.Electrochromic materials featured reversible color changes have been widely used in military,energy,screen display,automotive glass,goggles and other fields.Among them,polyaniline(PANI)has attracted much attention,due to its easier synthesis,good environmental stability,high color rendering,and low redox switching voltage.However,the strong intermolecular interactions and poor processability of PANI prevent its practical application.As model compounds of PANI,oligoanilines with well-defined structures have been extensively investigated due to their enhanced solubility,good electroactivity,excellent processability as well as color change similar to PANI.Recently,extensive efforts have been made to synthesize oligoaniline-containing polymers incorporated with other functional groups to achieve high electrochromic performance,multicolor properties and enhanced processability.To enlarge their practical application,it appears necessary to rationally design multifunctional oligoaniline-based materials.This thesis intends to synthesis multicolor electrochromic materials by introducing other types of electrochromic units into oligoaniline-based polymers utilizing the interaction and synergistic effect of two electrochromic motifs.Firstly,we intend to synthesize a novel dual-electrochromic polymer bearing both anodic electrochromic oligoaniline and cathodic electrochromic viologen units.The electrochemistry-assisted hydrolytic crosslinking method was used to obtain the dual-IV electrochromic polysiloxane,using the two hydrolysable siloxane precursors functionalized with oligoaniline and viologen.The resultant electrochromic polymer has good solubility and film-forming properties.A long-range electrochemical activity with low redox switching potentials have been disclosed in the measurement,attributed to the electron transfer between the viologen and the oligoaniline moieties.Moreover,the polymer reveals a robust three-dimensional networked molecular structure and strong covalent linkage with the ITO substrate,yielding good cycle stability.The resulting polymer bearing oligoaniline and viologen moieties demonstrates a wide voltage range and high optical contrast,with multiple colors changing from purple,transparent,green,and blue from the cathode region to the anode region.Secondly,a dual-electrochromic polymer was obtained through introducing oxidative coloring phenothiazine groups into oligoaniline-containing polymers via the electrochemistry-assisted hydrolytic crosslinking reaction.The resultant porous polymer film enables the electrolyte ions to be fully inserted/extracted accessibly,and the synergistic effect between the oligoaniline and phenothiazine expands the anode voltage range from-0.2 V to1.2 V.The electrochromic performance of the polymer is also significantly improved with the optical contrast of 53% at 700 nm.Meanwhile a multicolor change from light green,gray blue,grown red,and black purple has also been revealed.It can be confirmed that the integration of two electrochromic units into one polymeric architecture would be an effective strategy to obtain multicolor electrochromic materials.Finally,Prussian blue was deposited on the oligoaniline-based polysiloxane by an electrochemical deposition method,yielding the organic/inorganic composite electrochromic material.The porous channels in the composite are beneficial for electrolyte ions to be fully inserted/extracted accessibly.The strong covalent linkage between the polysiloxane material and the ITO substrate enables the material to undergo multiple cycles without being peeled off.The synergy between the composite materials improves the electrochromic properties of the PANI material,and the resulting film can convert from light yellow,to light green,to blue green,and finally to dark blue.In addition,integrating with its supercapacitor capability,a smart symmetrical capacitor device with energy level indicating functionality has been manufactured based on the aforementioned electrochromic composite.In summary,we have successfully synthesized several multicolor oligoanilinebased electrochromic materials.The resulting materials exhibit fascinating electrochromic behavior and multiple color changes,indicating that the integration of two electrochromic units into one polymer structure is an effective strategy for multicolor electrochromism.These oligoaniline-based multicolor electrochromic materials are expected to be used in smart electrochromic displays and intelligent electronic devices.