Engineering nanostructured polymer blends with controlled nanoparticle location for excellent microwave absorption: a compartmentalized approach

Abstract

In order to obtain better materials, control over the precise location of nanoparticles is indispensable. It is shown here that ordered arrangements of nanoparticles, possessing different characteristics (electrical/magnetic dipoles), in the blend structure can result in excellent microwave absorption. This is manifested from a high reflection loss of ca. -67 dB for the best blend structure designed here. To attenuate electromagnetic radiation, the key parameters of high electrical conductivity and large dielectric/magnetic loss are targeted here by including a conductive material [multiwall carbon nanotubes, MWNTs], ferroelectric nanostructured material with associated relaxations in the GHz frequency [barium titanate, BT] and lossy ferromagnetic nanoparticles [nickel ferrite, NF]. In this study, bi-continuous structures were designed using 50/50 (by wt) blends of polycarbonate (PC) and polyvinylidene fluoride (PVDF). The MWNTs were modified using an electron acceptor molecule, a derivative of perylenediimide, which facilitates π-π stacking with the nanotubes and stimulates efficient charge transport in the blends. The nanoscopic materials have specific affinity towards the PVDF phase. Hence, by introducing surface-active groups, an ordered arrangement can be tailored. To accomplish this, both BT and NF were first hydroxylated followed by the introduction of amine-terminal groups on the surface. The latter facilitated nucleophilic substitution reactions with PC and resulted in their precise location. In this study, we have shown for the first time that by a compartmentalized approach, superior EM attenuation can be achieved. For instance, when the nanoparticles were localized exclusively in the PVDF phase or in both the phases, the minimum reflection losses were ca. -18 dB (for the MWNT/BT mixture) and -29 dB (for the MWNT/NF mixture), and the shielding occurred primarily through reflection. Interestingly, by adopting the compartmentalized approach wherein the lossy materials were in the PC phase and the conductive materials (MWNT) were in the PVDF phase, outstanding reflection losses of ca. -57 dB (for the BT and MWNT combination) and -67 dB (for the NF and MWNT combination) were noted and the shielding occurred primarily through absorption. Thus, the approach demonstrates that nanoscopic structuring in the blends can be achieved under macroscopic processing conditions and this strategy can further be explored to design microwave absorbers.

Rational Design of Multilayer Ultrathin Nano‐Architecture by Coupling of Soft Conducting Nanocomposite with Ferrites and Porous Structures for Screening Electromagnetic Radiation

“…The preferential localization of nanoparticles in a selective phase of a heterogeneous polymer matrix is governed by various thermodynamic parameters. Interestingly though PC phase is thermodynamically more favored phase for dispersing MWCNTs over PVDF but MWCNTs are localized at PVDF phase due to its polarity mismatching . Selective dissolution test also corroborated with such observation.…”

“…It is well known that selective localization of nanoparticles in a given phase of an immiscible polymer blend is governed by several factors. As we discussed earlier that though PC is thermodynamically more favorable, but MWCNTs are generally localized in the PVDF phase possibly due to its higher polarity . Therefore, the removal of PC phase by dipping into chloroform does not alter the overall concentration and state of dispersion of MWCNTs which often has been observed during foaming to design porous structures (figure 2d).…”

Effect of blend ratio on the morphology and electromagnetic properties of nanoparticles incorporated natural rubber blends

“…Cao's work in polystyrene/poly(vinylidene fluoride) blends also indicates that improved thermal conductivity and flame retardancy can be achieved by controlling surface modification and selective localization of SiC nanoparticles [19]. Bose et al have incorporated dielectric/magnetic in different phase of polycarbonate and poly(vinylidene fluoride) blend, providing many folds microwave absorption than when they were localized in the same or in both the phases [20].…”

Significant promotion of porous architecture and magnetic Fe3O4 NPs inside honeycomb-like carbonaceous composites for enhanced microwave absorption

“…Hence, traditional efforts normally classied microwave-absorbing materials into two categories, namely, magnetic loss materials such as Fe, Co, Ni and alloys [9][10][11][12] and dielectric loss materials such as CuS, SiC, MnO 2 and conducting polymers. [13][14][15][16] Unfortunately, their high density greatly limits their potential applications despite their strong absorbing properties. Conveniently, to address this issue many carbonaceous materials such as carbon nanotubes (CNTs), carbon laments, carbon bers and chemically derived graphene have been used as composite materials for electromagnetic-wave absorbers owing to their light weight, exibility, high thermal conductivity, excellent mechanical properties and high electrical conductivity.…”