Constructing
Uniform Core–Shell PPy@PANI Composites
with Tunable Shell Thickness toward Enhancement in Microwave Absorption
- Publication date
- Publisher
Abstract
Highly uniform core–shell
composites, polypyrrole@polyaniline
(PPy@PANI), have been successfully constructed by directing the polymerization
of aniline on the surface of PPy microspheres. The thickness of PANI
shells, from 30 to 120 nm, can be well controlled by modulating the
weight ratio of aniline and PPy microspheres. PPy microspheres with
abundant carbonyl groups have very strong affinity to the conjugated
chains of PANI, which is responsible for the spontaneous formation
of uniform core–shell microstructures. However, the strong
affinity between PPy microspheres and PANI shells does not promote
the diffusion or reassembly of two kinds of conjugated chains. Coating
PPy microspheres with PANI shells increases the complex permittivity
and creates the mechanism of interfacial polarization, where the latter
plays an important role in increasing the dielectric loss of PPy@PANI
composites. With a proper thickness of PANI shells, the moderate dielectric
loss will produce well matched characteristic impedance, so that the
microwave absorption properties of these composites can be greatly
enhanced. Although PPy@PANI composites herein consume the incident
electromagnetic wave by absolute dielectric loss, their performances
are still superior or comparable to most PANI-based composites ever
reported, indicating that they can be taken as a new kind of promising
lightweight microwave absorbers. More importantly, microwave absorption
of PPy@PANI composites can be simply modulated not only by the thickness
of the absorbers, but also the shell thickness to satisfy the applications
in different frequency bands