Supramolecular Networks of Hyperbranched Poly(ether amine) (hPEA) Nanogel/Chitosan (CS) for the Selective Adsorption and Separation of Guest Molecules

Abstract

Supramolecular networks with selective adsorption for guest molecules were formed via dynamic hydrogen-bonding interactions between the carboxyl group-containing hyperbranched poly(ether amine) nanogels (hPEA-NG) and chitosan (CS). The hPEA-NG/CS supramolecular networks were physically cross-linked and were composed of hPEA-NGs dispersed within a crystallized CS matrix. An increasing CS content enhanced the mechanical properties of the hPEA-NG/CS supramolecular networks. The transparent hPEA-NG supramolecular networks did not disassemble in aqueous solutions with different pH values and organic solvents and were swollen with high weight fractions of water (WH2O = 0.95) in less than 30 s. The adsorptive behavior of seven fluorescein dyes and five azobenzene (azo) dyes onto the hPEA-NG/CS supramolecular networks was investigated. These hPEA-NG/CS supramolecular networks showed rapid adsorption for Rose Bengal (RB), Erythrosin B (ETB), Eosin B (EB), 4′,5′-dibromofluorescein (DBF), Ponceau S (PS) and Evans blue (EVB) dyes with high adsorption capacities (Qeq). The networks showed very low adsorption for calcein (Cal), fluorescein (FR), 4,5,6,7-tetrachlorofluorescein (TCF), and Bismarck brown (BBY) dyes. The adsorption process was found to follow pseudo-second-order kinetics. The different adsorptive behaviors for different dyes indicated the selective adsorption of the hPEA-NG/CS supramolecular networks for the azo and fluorescein dyes despite similar backbone structures and charge states. On the basis of the unique selective adsorption, the separation of mixtures of fluorescein dyes, such as RB/Cal, RB/FR, and PS/MR, was achieved using the hPEA-NG/CS supramolecular network as an adsorbent.