Synthesis, Characterization And Electromagnetic Wave Absorbing Properties Of Chiral Schiff Base Polymers

Chiral absorbing material is a new kind of electromagnetic absorbing material with helical structure. Compared with ordinary absorbing material, Chiral absorbing materials has three kinds of advantages: Firstly, the helical structure can cause the cross polarization of electromagnetic field and get a better absorbing performance; Secondly, the chiral parameters are easier to be adjusted than the electromagnetic parameters, which can meet the requirements of no reflection on wide bands. In addition, the frequency sensitivity of the chiral material is lower than the electromagnetic permeability, which is easy to obtain broadband absorbing. Chiral poly Schiff base is a new type of chiral conductive polymer absorbing material, which combines the advantages of chiral absorbing material and conductive polymer absorbing material. It has very big potential in improving absorbing performance and extend absorbing bandwidth.L-lysine and L-arginine were used as chiral sources, 13 kinds of chiral poly Schiff bases and their silver salts were synthesized. The chiral poly Schiff base silver salt/Fe3O4 composites were prepared by solution blending method. The conductivities and electromagnetic parameters of chiral poly Schiff base silver salts and composite materials wer analyzed, then the absorbing performances were calculated and analyzed. There are several main works below:(1) A large number of literatures were consulted. The research progress of the chiral absorbing material and poly Schiff base absorbing material was summarized. The synthesis of chiral poly Schiff bases and their salts were introduced.(2) 8 kinds of L-lysine chiral poly Schiff bases and their silver salts were synthesized. The structures were characterized through IR, element analysis and optical rotation. The silver ion contents of chiral poly Schiff base silver salts were determined. Their electrical conductivities were measured using a four-point tester, the conductivity of chiral poly-(L-lysine(2,3-butanedione)) Schiff base silver salt can reach 3.7 × 102 S/cm. The electromagnetic parameters and absorbing performances of some chiral poly Schiff base silver salts were analysized, the absorbing performance of chiral poly-(L-lysine(p-benzoquinone)) Schiff base silver salt is best, the maximum reflection loss can reach-45.9 d B at a thickness of 5 mm and a frequency of 10.7 GHz.(3) 5 kinds of L-arginine chiral poly Schiff bases and their silver salts were synthesized. The structures were characterized through IR, element analysis and optical rotation. The silver ion contents of chiral poly Schiff base silver salts were determined. Their electrical conductivities were measured using a four-point tester, the conductivities of chiral poly Schiff base silver salts have at least 3 orders of magnitude improvement than chiral poly Schiff bases.(4) The binary composite materials of chiral poly-(L-lysine(2,3-butanedione)) Schiff base silver salt/Fe3O4 were prepared by solution blending method. The achiral poly-(DL-lysine(2,3-butanedione)) Schiff base silver salt/Fe3O4 composite material was prepared by the same method. The conductivities and electromagnetic wave absorbing properties of the composite materials were studied. The maximum reflection loss of chiral poly-(L-lysine(2,3-butanedione)) Schiff base silver salt/Fe3O4 binary composite material can reach-26.5 d B at a thickness of 5.5 mm and a frequency of 14.9 GHz, which is better than that of achiral poly-(DL-lysine(2,3-butanedione)) Schiff base silver salt/Fe3O4 binary composite material. The carbon nanotubes/Co0.5Ni0.5Fe2O4 composite was synthesized by hydrothermal method, the(carbon nanotubes/Co0.5Ni0.5Fe2O4)/poly-(L-lysine(p-benzoquinone)) Schiff base silver salt ternary composites were prepared by solution blending method. The structures and morphologies of the composite materials were characterized and analysized by XRD and TEM. The ratios of poly-(L-lysine(p-benzoquinone)) Schiff base silver salt have a great influence on the conductivity properties and abosorbing performances of the composite materials. The ternary composite material-1 has the strongest reflection loss of-33.3 d B at a thickness of 1.5 mm and a frequency of 13.2 GHz, and has the reflection loss of below-10 d B at all thicknesses of 1 – 5.5 mm. The ternary composite materials have better absorbing performances than the binary composite materials...