Preparation And Microwave Absorption Properties Of Conductive Polyaniline And Its Nanocomposites

As a typical conductive polymer,polyaniline(PANI)possesses the advantages of controllable conductivity,designable morphology and structure,facile synthesis and low density.Herein,PANI has gradually become one of the research hotspots in the field of electromagnetic wave absorbing materials.However,it still remains great challenges to maximize the microwave absorbing performance of PANI,and make it to be a new generation of novel microwave absorber.Thus,based on designable structures property of conductive PANI,superhelical chiral PANI and porous structured PANI hybrids have been prepared.The morphology and structures of as-prepared samples have been analyzed via multi-scale characterization methods.The electromagnetic parameters of absorbers are detected by vector network analyzer(VNA).Furthermore,the relationship between structures and microwave absorption properties has been systematically discussed.The investigation results include the following aspects:Firstly,superhelical chiral PANI(SC-PANI)has been synthesized via in situ polymerization coupling with self-assembly method using chiral camphor sulfonic acid(S-CSA)as dopent and chiral inducer.The superhelical structure and chiral characteristic have been investigated by scanning electron microscope(SEM),transmission electron microscope(TEM)and circular dichroic spectrometer(CD)instruments.The magnetic and microwave absorption properties of SC-PANI are investigated via vibrating sample magnetometer(VSM)and VNA.The results show that as-prepared SC-PANI exhibits apparent superhelical structures and chiral characteristic Moreover,VSM results show that SC-PANI possesses superior magnetic performance Compared to conventional PANI,SC-PANI(loading ratio in wax is 30 wt%,thickness is 1.7 mm)possesses enhanced microwave absorption performance with the minimum RL(RLmin)value of-31.7 dB at 11.7 GHz and the frequency bandwidth corresponding to the RL values less than-10 dB are 3.8 GHz(from 10 to 13.8 GHz).These solid results verify that multi-loss microwave absorption mechanism of sole-component PANI can be achieved by superhelical morphology design and chiral structure construction,thus promoting its microwave absorption ability.Secondly,owing to the designable structure of conductive PANI,for improving the impedance mismatching of vapor grown carbon fiber(VGCFs).Homogeneous porous structured PANI decorated VGCFs hybrids(p-VGCF@PANI)have been fabricated via sacrificial templates and in situ polymerization method.The morphologies,structures and synthesis mechanism of p-VGCF@PANI hybrids have been demonstrated.The electromagnetic parameters,Impedance matching ratio and microwave absorption properties of p-VGCF@PANI have been analyzed.The results show that porous PANI are homogeneously decorated onto the surface of VGCFs using MnO2 as porous templates and initiator.p-VGCF@PANI demonstrates enhanced impedance matching performance and superior microwave absorption properties with the RLmin value of-55.9 dB at 10.3 GHz and matching thickness of 1.33 mm(filler loading ratio in wax is 18 wt%),where the effective absorption region located at 9.4-11.6 GHzFinally,For further investigating and expanding the practical application of high performance powdered electromagnetic wave absorbers.A universal approach involving chemical adsorption and dip coating methods are proposed to address the critical issue for hybridizing porous VGCF@PANI with flexible polyurethane sponge(PUS)as practical electromagnetic absorption material(HP-VGCF@PANI-PUS).The mechanical compression and tunable thickness performance of HP-VGCF@PANI-PUS nanohybrids are utilized to tune its electromagnetic parameters and microwave absorption performance.The results demonstrate that HP-VGCF@PANI-PUS not only possess excellent mechanical compression performance,but enhanced microwave absorption propertie.The shape recovery of HP-VGCF@PANI-PUS nanohybrids was maintained at 100%after 10 cycles between 0%and 80%strain through cyclic compression tests.Moreover,the hybrids exhibited interesting dual absorption properties with RLmin of-28.8 dB and-5.5 dB at frequencies of 8.5 GHz and 8.7 GHz,respectively.