Preparation Of Polymer/dabcoHReO₄ Composite Piezoelectric Materials And Investigation Of Their Properties

With the coming of the artificial intelligence era,flexible electronic skins and wearable devices have attracted extensive attention.Piezoelectric polymer has become one of the key materials for preparing flexible piezoelectric sensors because of its flexibility and good piezoelectric properties.However,at present,the comprehensive properties of piezoelectric polymers can not meet the requirements of preparing flexible electronic skins and wearable devices.Developing efficient preparation methods of piezoelectric polymer composites,deeply understanding the structure-activity relationship of piezoelectric polymer composites and effectively improving their comprehensive properties have become important research topics in the field of chemistry and physics.Herein,we prepared two kinds of polymer/molecular ferroelectric piezoelectric composites with good dispersion by exploring intermolecular hydrogen bond interactions,studied the influence law of intermolecular hydrogen bond interactions and interface coupling interactions on piezoelectric properties,developed piezoelectric polymer composites and piezoelectric sensors with flexible and stretchable characteristics,and explored their applications in the field of flexible electronic devices,which was of great significance for the development of flexible electronic skins and wearable devices.The main research results are as follows:(1)Preparation of poly(vinylidene fluoride)/dabcoHReO4 composite piezoelectric materials and the research of propertiesPoly(vinylidene fluoride)(PVDF)will form a variety of crystal forms when it crystallizes,however,the high β-phase crystal content is one of the preconditions for its good piezoelectric properties.In this chapter,molecular ferroelectrics-dabcoHReO4(DH)acted as fillers,we prepared PVDF/DH composite piezoelectric materials,systematically regulated the content of DH,studied the effect of hydrogen bond interactions between PVDF and DH on the crystal transformation of PVDF,and established the corresponding relationship between DH content and piezoelectric output voltage.The content of β-phase crystal was increased to 95%,and the residual polarization intensity was more than 56 mC/m2.(2)Preparation of transparent poly(vinylidene fluoride)/dabcoHReO4 composite piezoelectric films and the research of propertiesDue to light scattering,the optical transparency of PVDF/DH composite piezoelectric films is poor.In order to improve the transparency and preparation efficiency of PVDF/DH composite piezoelectric films and devices,the large-area preparation methods of PVDF/DH composite films and the methods of reducing the surface roughness of films were developed in this chapter,the relationship between water washing conditions,heat treatment temperature and the surface roughness of films and the relationship between the surface roughness of films and transparency were studied,the rapid preparation of composite films with good piezoelectric performance(the piezoelectric strain coefficient d33≈-29 pC/N)and transparency(the visible light transmittance>90%)and piezoelectric sensors was realized,and the adhesion of films and the stability of devices were improved.(3)Preparation of patterned poly(vinylidene fluoride)/dabcoHReO4 composite piezoelectric films and the research of propertiesIn order to improve the piezoelectric performance and pressure detection sensitivity of the flexible piezoelectric sensors based on PVDF/DH composites,a micro-nano patterning method was developed in this chapter,which successfully copied the micro-nano structures of calathea zebrine leaves to the surface of PVDF/DH composite films,the d33 value of PVDF/DH composite films was increased to-36 pC/N,the sensitivity of the flexible piezoelectric sensors was improved to 201.5 mV/kPa.The sensitivity of micro-nano patterned piezoelectric sensor was 6 times than that of non-structured piezoelectric device.Theoretical analysis and simulation results show that the improvement of sensitivity is mainly due to the reduction of Young’s modulus and the increased strain rate of the materials.(4)Preparation of stretchable polymer/dabcoHReO4 composite piezoelectric gels and the research of propertiesIn order to improve the stretchable properties of piezoelectric polymer composites,DH and poly(ethylene glycol)(PEG)-based poly(urethane-urea)(PUU)gels were taken as the research objects in this chapter,stretchable PUU/DH composite piezoelectric gels with good transparency and piezoelectric properties were designed and prepared by exploring the hydrogen bond interactions between DH and PEG.The transparency of the films can reach more than 90%,the piezoelectric coefficient d33 can reach-62 pC/N,and the tensile strain rate can reach more than 1000%.The influence of the interface coupling between PUU and DH on the piezoelectric properties was further studied,and the application of PUU/DH composite piezoelectric gels in the field of flexible electronic skins was explored.