Synthesis, Electrochromic, And Gel Properties Of Oligomeric (3,4-ethylenedioxythiophene) Derivatives

Poly?3,4-ethylenedioxythiophene??PEDOT?and its derivatives have good photoelectric properties and carrier transport ability.At present,the researches on PEDOT in the electrochromic field mainly focus on two aspects.One is the copolymers prepared from EDOT and other monomers.The other is the composites of PEDOT and inorganic materials.However,there are few studies on oligo-EDOT and its derivatives in the electrochromic field.In this paper,a series of oligo-EDOT derivatives are designed and synthesized,which are:2,5-di?methyl benzoate?-3,4-ethylenedioxythiophene?1EDOT-2B-COOCH₃?,5,5'-di?methyl benzoate?-2,2'-bi?3,4-ethylenedioxythiophene??2EDOT-2B-COOCH₃?,5,5''-di?methyl benzo-ate?-2,2':5',2''-ter?3,4-ethylenedioxythiophene??3EDOT-2B-COOCH₃?,and 5,5'''-di?methyl benzoate?-2,2':5',2'':5'',2'''-quater?3,4-ethylenedioxythiophene??4EDOT-2B-COOCH₃?,2,5-di-?N-octadecyl benzoyl?-3,4-ethylenedioxythiophene(1EDOT-2B-NC₁₈),5,5'-di?N-octadecyl benzoyl?-2,2'-bi?3,4-ethyle-nedioxythiophene?(2EDOT-2B-NC₁₈),and 5,5'''-di?N-octadecyl benzoyl?-2,2':5',2'':5'',2'''-quater?3,4-ethylenedioxythiophene?(4EDOT-2B-NC₁₈).They are characterized by MS,NMR,and IR.Molecular structures of target compounds are as follows:The UV-vis absorption spectra,fluorescence spectra and cyclic voltammograms of these oligo-EDOT derivatives were determined.Their optical bandgap,electrochemical bandgap and fluorescence quantum efficiency were calculated.Using these oligomers as active layers,flexible organic electrochromic devices?ECDs?are fabricated.The device structure is ITO-PET/active layer/conducting gel/ITO-PET.Electrochromic properties of these oligo-EDOT derivatives were studied,respectively.These oligomers exhibit reversible color changes upon electrochemical doping and dedoping.The highest optical contrast is exhibited by4EDOT-2B-COOCH₃,which is 75.2%at 700 nm.The gel properties of three amide oligomers are studied.Both 1EDOT-2B-NC₁₈ and 2EDOT-2B-NC₁₈ have the ability to form gel in different solvents.The electrochromic properties of the gel were investigated.The gel based on 2EDOT-2B-NC₁₈ can exhibit reversible color changes from light yellow to orange.