Facile Preparation of Nanofibrillar Networks of Ureido-Chitin Containing Ureido and Amine as Chelating Functional Groups

Aerogels of polysaccharides with chelating functions can be useful as supports in many applications because of their hosting properties. This work demonstrates a facile method for the preparation of aerogels of chitosan derivative ureido-chitin, containing ureido functional groups. The nanofibrillar networks of ureido-chitin were produced by the nucleophilic addition of amine groups of chitosan with isocyanic acid prepared in situ. The presence of ureido functional groups was confirmed by FTIR, solid-state CP-MAS C-13 and N-15 NMR analyses. No crosslinking of molecular chains was observed. The maximum degree of ureido functional groups was estimated to be about 66 %. Characterization by powder XRD confirmed that the polymer chains self-assembled, with the chitin polymers oriented in a highly ordered crystalline structure. The nanofibrillar networks showed no solubility under either aqueous acidic or alkaline conditions. Bio-based hosting materials of this kind with two different hosting functional groups, ureido and amine, can potentially be utilized for a wide range of applications in aqueous medium, including filters, catalysis and biomedicine.