| Ferroelectric materials have gained wide attention by means of specific spontaneous polarization property since the discovery of ferroelectricity in the Rochelle salt in the 1920s.Ferroelectric materials also have a series of special properties,such as excellent electricity,nonlinear optics,electro-optics,etc.,which can be used to make different functional devices,and it is expected to make integrated devices through the integration or combination of ferroelectric materials and other materials.In the past two decades,due to the workability,high flexibility and good compatibility of organic materials,researchers have been trying to adjust and improve the ferroelectric properties of PVDF composites by optimizing the conformation and combining them with inorganic or organic fillers.However,the low dielectric constant of PVDF-inorganic ferroelectric materials restricts the further development of composite materials.Although the addition of conductive polymer will improve the overall conductivity of the material,the percolation effect will cause the material to break down under the electric field,thus losing the ferroelectric property.At present,there are few studies on conducting polymer free-standing thin films as ferroelectric materials.Therefore,it is of great significance for the expansion of ferroelectric materials and the exploration of application prospect to prepare ferroelectric conductive polymer films by simple methods.In this paper,three kinds of polymers with ferroelectric properties were synthesized by electrochemical polymerization:Poly（dibenzo-14-crown ether-4）（PDBC-14）,poly（dibenzo-15-crown ether-5）（PDBC-15）and poly（dibenzo-18-crown ether-6）（PDBC-18）,The electrochemical and dielectric ferroelectric properties of the three polymer films were systematically investigated,and the relationship between the molecular structure of the polymers and their properties was revealed.The specific research contents and results are as follows:1.Poly（dibenzo-18-crown ether-6）（PDBC-18）was synthesized by electrochemical polymerization in pure boron trifluoride ether system and the film was prepared.The redox properties,cyclic voltammetry stability,microstructure,composition and thermal stability of polymer films were studied in detail by electrochemical analysis,morphology analysis,infrared absorption spectroscopy and thermogravimetric analysis.It is found that PDBC-1 8 has good redox activity and cyclic voltammogram stability in BFEE,and the conductivity of PDBC-1 8 film is2.0×10-2S cm-1.PDBC-18 polymer films have relatively regular cauliflower morphology,and have better heat resistance within 400℃.In addition,the ferroelectric dielectric properties of PDBC-18 thin films were studied by ferroelectric-dielectric spectrometer.PDBC-18 films show remarkable ferroelectric properties.Under the reversible changing electric field,the PDBC-18 thin film generates hysteresis loops,and the shape of the hysteresis loops and the residual polarization intensity Pr increase with the increase of the range of the changing field intensity.When the electric field intensity varies from±400 k V cm-1to±1200 k V cm-1,the corresponding residual polarization intensity Pr varies from 0.11 to 2.16μC cm-2.PDBC-18 films show general dielectric properties.In the range of 102to 106Hz,PDBC-18 films show a general dielectric constant of 3.7 to 3.9.And its dielectric loss value is low:2.4 to 0.036.2.Poly（dibenzo-15-crown ether-5）（PDBC-15）was synthesized by electrochemical polymerization in pure boron trifluoride ether system and the film was prepared.The redox properties,cyclic voltammetry stability,microstructure,composition and thermal stability of polymer films were studied in detail by electrochemical analysis,morphology analysis,infrared absorption spectroscopy and thermogravimetric analysis.It is found that PDBC-1 5 has good redox activity and general cyclic voltampere stability in BFEE,and PDBC-15 has almost no conduction between the film surfaces.PDBC-15 polymer films have relatively regular cauliflower morphology,and have better heat resistance within 390℃.In addition,the ferroelectric dielectric properties of PDBC-15 thin films were studied by ferroelectric-dielectric spectrometer.The PDBC-15 films exhibit general ferroelectric properties.Under the reversible changing electric field,the PDBC-15 thin film generates hysteresis loops,and the shape of the hysteresis loops and the residual polarization intensity Pr increase with the increase of the range of the changing field intensity.When the electric field intensity varies from±400 k V cm-1to±1200 k V cm-1,the corresponding residual polarization intensity Prvaries from 0.039 to 0.35μC cm-2.PDBC-15 films show good dielectric properties.In the range of 102to 106Hz,PDBC-18 films show a higher dielectric constant:15.0 to 13.3.And its dielectric loss value is low:0.015 to 0.033.3.Poly（dibenzo-14-crown ether-4）（PDBC-14）was synthesized and thin films were prepared by electrochemical polymerization in pure boron trifluoride ether system.The redox properties,cyclic voltammetry stability,microstructure,composition and thermal stability of polymer films were studied in detail by electrochemical analysis,morphology analysis,infrared absorption spectroscopy and thermogravimetric analysis.It is found that PDBC-1 4 has good redox activity and cyclic voltammogram stability in BFEE,and the interfacial conductivity of PDBC-14film is almost zero.PDBC-14 polymer films have relatively chaotic cauliflower morphology,and have better heat resistance within 370℃.PDBC-14 films show remarkable ferroelectric properties.Under the reversible changing electric field,the PDBC-14 film generates hysteresis loops,and the shape of the hysteresis loops and the residual polarization intensity Pr increase with the increase of the range of the changing field intensity.When the electric field intensity varies from±400 k V cm-1to±1200 k V cm-1,the corresponding residual polarization intensity Prvaries from 0.019to 0.10μC cm-2.PDBC-14 films show good dielectric properties.In the range of 102to 106Hz,PDBC-18 films show a higher dielectric constant:12.0 to 9.7.And its dielectric loss value is low:0.02 to 0.01. |
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