Chiral polyaniline with superhelical structures for enhancement in microwave absorption

Abstract

Chiral polyaniline (PANI) with superhelical structure is successfully synthesized via in situ polymerization using chiral acid as dopant and self-assembly technique. The morphology and structure were characterized by scanning electron microcopy, transmission electron microscopy, fourier transform infrared spectra, circular dichroism, X-ray diffractometer and X-ray photoelectron spectra, which demonstrate polyaniline has chirality and superhelical structure. A possible formation process of the superhelical structure was also discussed. The microwave absorption properties of superhelical chiral PANI was investigated in the frequency range of 2–18 GHz. The results indicated that the superhelical chiral PANI exhibit substantially enhanced electromagnetic losses compared to conventional PANI. The minimum reflection loss (RL) of the superhelical chiral PANI can reach −31.7 dB at 11.7 GHz, and the bandwidth less than −10 dB is 3.8 GHz with absorber thickness of 1.7 mm. The enhanced microwave absorbing property can be attributed to multi-loss mechanisms, good impedance matching and the cross-polarization effects resulting from the superhelical structure and chirality.