Facile and large-scale synthesis of functional poly(m-phenylenediamine) nanoparticles by Cu2+-assisted method with superior ability for dye adsorption

Abstract

Traditional chemical oxidative polymerization, with the procedure of gradually adding the oxidant, generally produces amine-containing conjugated polymer (NCP) microparticles. In this paper, an improved method has been developed through using a small amount of Cu²⁺ prior to the polymerization for large-scale synthesis of poly(m-phenylenediamine) (PmPD, one typical NCP) nanoparticles. The Cu-monomer/oligomer complex nanoparticle structures formed before the polymerization are suitable intermediates to activate the polymerization and induce the morphology evolution of the PmPD nanostructures. A possible mechanism is that Cu ions at the centre of the complex mediate the electron transfer from ligand to persulfate oxidant, as analyzed by comparative experiments; Fourier transform infrared spectrometry (FTIR) and open-circuit potential of the polymerization. During the growth of macromolecular chains, the Cu ions are gradually released into the bulk solution from the complex. The nano-sized PmPD was used to adsorb a dye (Orange G) and showed high adsorbance of 387.6 mg g⁻¹, which is on average 200 mg g⁻¹ more than that of the microparticles.