Facile preparation of polyethylene glycol-functionalized chitosan aerogel particles

Kurzfassung

Porous materials of functionalized chitosan materials receive great attention in limitless applications such as biomedicine, filters, purifiers, binders, etc., as the new functional groups can enhance the chitosan properties. Preparation and characterization of functionalized chitosan aerogel beads have been investigated in the present study. Polyethylene glycol diglycidyl ether (PEGDGE) was used as a functionalizing agent. The ring opening SN1 addition reaction took place between the epoxy rings of PEGDGE and the amine functional groups of chitosan at acidic aqueous condition below pH 6. This proposed reaction mechanism was confirmed by the FTIR spectral data where the amine vibrational bands disappear when the PEGDGE concentration was increased. The aerogel beads were prepared by employing the conventional syringe dropping technique, letting the droplets of chitosan solution to fall into the sodium hydroxide bath. After washing and solvent exchange processes, the spherical beads were dried in an autoclave under supercritical CO2 condition (aerogel) and freeze-drying method (cryogel). The aerogel beads showed a linear trend with different physical properties while increasing the concentration of PEGDGE. The aerogel beads were characterized by density analyzer methods (skeletal and envelope density), BET specific surface area, microstructure analyses using SEM, FTIR, powder XRD, DSC and TGA. The functionalized aerogel beads of chitosan were pure, no impurities were found and the materials showed the poorly crystalline peaks of chitosan. This study showed the preparation of chitosan aerogel beads having various degree of functionalization, open porous structure, interconnected nanofibrillar network and high specific surface area (130 – 230 m2·g-1). These aerogel beads may provide an alternative way of utilizing the nanostructured matrix of functionalized chitosan instead of monoliths for various applications.