Polymer-assisted dispersion of carbon nanotubes and silver nanoparticles and their applications
Abstract
We report a family of novel dispersants that are highly effective for finely dispersing carbon nanotubes (CNT) and silver nanoparticles (AgNPs) in aqueous medium. The imide functionalized dispersants were prepared from the amidation of diamine and dianhydrides such as 4,4′-oxydiphthalic dianhydride, 4,4′-carbonyldiphthalic anhydride and pyromellitic dianhydride. The poly(oxyalkylene)-diamines with different backbones including poly(oxypropylene) (POP) and poly(oxyethylene) (POE) were allowed to react with dianhydride at 2 : 1 to 7 : 6 molar ratio under the conditions of condensation at 150 °C. The amidoacid intermediates were readily converted into cyclic imide structures as the thermodynamic products, as characterized by Fourier transform infrared. These copolymers were screened for the dispersed ability for CNT in a DMF–H2O mixture, characterized by UV-visible absorption. The comparison identified that the amine-terminated and POE-segmented imide (POE-imide) at >6 : 5 of amine/anhydride ratio was more effective for dispersing CNT than the anhydride-terminated imide analogs and POP-segmented imide. The tandem procedures of dispersing CNT and then AgNPs were developed by in situ reduction of AgNO3 in the presence of the POE-imide dispersant. As a result, the homogeneous dispersion of mixtures of CNT-tethered AgNPs (20–30 nm in diameter) and free AgNPs (8–30 nm) was prepared. Furthermore, the AgNPs/CNT nanohybrid was also isolated by centrifugation and removal of the free AgNPs, and characterized by transmission electron microscopy and we prepared a conductive film (10 μm) with the conductivity of 103 to 105 S cm−1 by controlling the annealing temperature in air.