The Synthesis,polymerization And Capacitive Properties Of Functionalized Flexible Chains Bridging Two EDOT Units

Conductive polymers?CPs?are one of the electrode materials for supercapacitors,ultra-long cycling stability of conducting polymers holds an essential role in practical application of supercapacitors,for it can greatly reduce the expenses of the maintena nce and the substitutes due to the ultra-stable charge and discharge.However,CPs often exhibit powdery state or fragile films,furthermore,the susceptible volumetric changes?swel ing or shrinkage?during the intercalating and deintercalating process of electrons and electrolyte ions greatly result in the poor cyclic stability,which have been considered as the major drawbacks for CPs in the application of supercapacitors.As one of the most promising CPs,Poly?3,4-ethylenedioxythiophene??PEDOT?is finding wide use because of its outstanding features,such as its positive?p-?and negative?n-?doping characteristics,wider potential range,and excellent environmental stability.But even so,owing to its rigid structure,insoluble and infusible nature,pure PEDOT films are difficult to prepare into freestanding state by chemical and electrochemical methods.Herein,this paper uses a simple strategy of introducing alkoxy,ether,ester,and amide flexible chains for bridging two EDOT units to form four novel EDOT derivatives,which could then be electrodeposited readily by one step to produce freestanding and flexible films.The structures,morphologies,thermal stabilities,mechanical flexibility,and capacitive performance of the fabricated films were detailedly investigated with comparisons.The main contents of this research are as follows:?1?1,6-bis??2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl?methoxy?hexane?BEDTH?is synthesized by a simple strategy of introducing flexible alkoxy chains with six carbon atoms for bridging two EDOT units.The corresponding polymer?PBEDTH?can be obtained by electrodepositing potentiostatically in DCM containing 0.02 M monomer and 0.1 M Bu₄NPF₆ at 1.5 V.The structure of BEDTH and PBEDTH is confirmed by H¹ NMR and FT-IR.The TGA and DMA results ilustrate that the PBEDTH film possesses high thermal stability and mechanical properties.The electrochemical results indicate that the PBEDTH film has a highest specific capacitance of 73.9 F g^-1at 10 mV s^-1 in ACN containing 0.1 M Bu₄NPF₆.Besides,the asymmetric supercapacitor based on PBEDTH//PEDOT shows an excelent capacitance retention rate of 92.7%after5000 cycles.?2?1,12-bis?2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl?-2,5,8,11-tetraoxadodecane?BEDTG?is synthesized by introducing flexible ether chains with six carbon atoms for bridging two EDOT units.The corresponding polymer?PBEDTG?is likewise electrodeposited potentiostatically in DCM containing 0.1 M Bu₄NPF₆ at 1.5 V.The results of H¹ NMR and FT-IR testify the correct structure of BEDTG and PBEDTG.The DMA results ilustrate that the PBEDTH film possesses higher mechanica l properties than PBEDTH.The electrochemical tests in ACN containing 0.1 M Bu₄NPF₆ indicate that the PBEDTG film has a highest specific capacitance of 84.2 F g^-1at 10 mV s^-1,which is higher than PBEDTH.However,the capacitive retention of the asymmetric supercapacitor based on PBEDTG//PEDOT is 80.4%after 5000 cycles,which is lower than PBEDTH//PEDOT.?3?Bis??2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl?methyl?adipate?BEDTE?is synthesized by the same strategy of introducing flexible ester chains with six carbon atoms for bridging two EDOT units.The corresponding polymer?PBEDTE?is obtained by potentiostatically electrodepositing 0.02 M BEDTE in DCM containing0.1 M Bu₄NPF₆ at 1.5 V.The structure of BEDTE and PBEDTE is confirmed by H¹NMR and FT-IR.The results from DMA data demonstrate that the mechanica l properties of PBEDTE is worse than PBEDTG but better than PBEDTH.The electrochemical test results in ACN containing 0.1 M Bu₄NPF₆ indicate that the PBEDTG film has a highest specific capacitance of 76.8 F g^-1at 10 mV s^-1,which is between the values of PBEDTH and PBEDTG under the same scan rate,the capacitance retention of the asymmetric supercapacitor based on PBEDTE//PEDOT is86.7%after 5000 cycles,which is lower than PBEDTH//PEDOT but higher than PBEDTG//PEDOT.?4?N,N-bis??2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl?methyl?adipa-mide?BEDTA?is synthesized by bridging two EDOT units with the flexible hexyl chains that company with two functionalized amide groups.The corresponding polymer?PBEDTG?is likewise prepared by electrodepositing potentiostatically in DCM containing 0.1 M Bu₄NPF₆ at 1.5 V.The results of H¹ NMR and FT-IR testify the correct structure of BEDTA and PBEDTA.The TG and DMA results il ustrate that the PBEDTH film possesses highest thermal stability and mechanical property among the four polymer films.The electrochemical tests in ACN containing 0.1 M Bu₄NPF₆indicate that the PBEDTG film has a highest specific capacitance of 100 F g^-1at 10 mV s^-1,which is also the highest value among the four polymer films.Besides,the cycling life of PBEDTA is 98.5%after 5000 cycles,demonstrating that the PBEDTA films are the most suitable conducting polymers for flexible supercapacitors among the four as-prepared polymers.