for microwave-absorbing (MWA) applications. There is growing demand for MWA materials in the fields of radar detection, electromagnetic shielding and electronics. Upon exposure to microwave fields, carbon nanotubes efficiently attenuate incident propagating waves and evolve tremendous heat. This ability to heat as powerful microwave susceptors could be useful in food packaging, where coatings are used to heat and brown foods during microwave cooking. Conventional MWA materials such as aluminum present some health concerns. [9] Polymer composites incorporating CNT offer a wide range of applications and the possibility of tuning desirable properties, including MWA, by varying nanotube loading. Although many studies have observed the microwave absorbing behavior of CNT bulk nanocomposites, there is little research on how such composites behave when their thickness is on the scale of nanometers. [1,[10][11][12] The present work investigates the microwave absorption of thin films composed of anionically stabilized carbon nanotubes and a polycation, deposited layer-by-layer (LbL). LbL assembly involves the "bottom-up" fabrication of thin films by alternately exposing a substrate to positively and negatively charged materials in aqueous suspensions. Film thickness is controlled by the number of deposition cycles, with each positive and negative layer pair referred to as a bilayer (BL). [13,14] This is a powerful coating technique, capable of coating many substrates to impart a variety of properties such as energy generation, [15][16][17][18] antimicrobial, [19,20] gas barrier, [21,22] and flame retardancy. [23,24] LbL assembly provides an elegant approach to constructing thin CNT composites on complex substrates with high loading and exceptional electrical conductivity. [25][26][27][28][29][30][31][32][33][34] In the present study, CNT-based films were deposited on polyester (poly(ethylene terephthalate), PET) substrates using LbL assembly under ambient conditions and aqueous suspensions. These sub-300 nm thick coatings provide an attractive alternative to common MWA coatings, such as magnetic materials or ceramic ferroelectrics, which require more complex processing and add undesirable mass. [35] Multilayer thin films composed of either single-walled (SWNT) or multiwall carbon nanotubes (MWNT), stabilized by deoxycholate, were paired with poly(diallyldimethylammonium chloride) [PDDA] and deposited according to a previously Carbon nanotubes have emerged as highly effective materials for microwave absorbing applications due to their high electrical conductivity, large aspect ratio, and high temperature stability against oxidation and corrosion. Ultrathin films are fabricated through layer-by-layer deposition of carbon nanotubes and poly(diallyldimethyl ammonium chloride) from aqueous suspensions under ambient conditions. The number of immersion cycles controls the assembled thickness of these coatings, which provides an effective means of precisely tailoring their electrical properties and thermal response to microwaves....
