Two-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 (similar to 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 mu m thickness and 0.45 g/cm(3) 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 cm(3) g(-1), respectively. Additionally, the nanocomposites remain thermally stable up to 500 degrees C in oxidative environment and possess an appreciably high storage modulus of 3.113 GPa at 50 degrees C. These low-density conductive polyimide films, therefore, present great prospects in shielding against electromagnetic interference under extreme conditions.
