Vigilancia Tecnológica

Guar Gum induces anisotropic growth of silver nuclei into two?dimensional silver nanoplates under ambient conditions. The synthetic protocol is quick, scalable, facile, and yields highly pure elemental silver capable of imparting appreciable conductivity to high?performance polymers such as polyimide. The composite material is suitable for  protection against electromagnetic interference in advanced technologies.AbstractTwo?dimensional (2D) silver nanoplates are chemically synthesized in the presence of guar gum – a naturally occurring biopolymer. The polymer directs anisotropic growth of silver nuclei into high aspect ratio nanoplates spanning 4500?±?500?nm lateral length with thickness as small as 40?±?10?nm. After a thorough investigation of the reaction parameters (temperature, precursor to reductant ratio, and polymer quantity) on the morphology of the product, a scalable synthetic protocol to achieve good yields (95%–98%) of highly pure (~100%) 2D silver nanoplates (AgNPls) in a facile, inexpensive, room temperature, aqueous phase chemical reaction of only about 5?min is devised. The optimized AgNPls induce appreciable conductivity of 5.5?±?0.38?S/cm in polyimide at only 12?wt% loading. Consequently, the resulting polymer nanocomposite (containing 12?wt% AgNPls), at only 130?±?15??m thickness and 0.45?g/cm3 density, effectively blocks electromagnetic radiation in X?band with a total shield effectiveness of about 10?dB resulting in substantially high specific shielding effectiveness and absolute shielding effectiveness of 22.48 and 1729.23?dB?cm3?g?1, respectively. Additionally, the nanocomposites remain thermally stable up to 500°C in oxidative environment and possess an appreciably high storage modulus of 3.113?GPa at 50°C. These low?density conductive polyimide films, therefore, present great prospects in shielding against electromagnetic interference under extreme conditions.