Synthesis and characterization of a dendrimeric polycitrate-alumoxane nano composite

• A dendrimeric hyper-branched polycitrate-alumoxane nano composite has been synthesized.
• The polycitrate-alumoxane proved to be a hydrophilic material.
• The mechanism of polybranching and dendrimerization has been proposed and discussed.
• Thermal degradation of nano composite led to the formation of gibbsite.

This work illustrates the synthesis of a three-dimensional dendrimeric hyper-branched alumoxane nanostructure, named as polycitrate-Alumoxane (PC-A), through condensation reactions between the hydroxyl groups of boehmite nanoparticles (BNs) and the carboxylic groups of citric acid (CA), producing carboxylate alumoxane linkages. FTIR, SEM, TEM, XRD and TG–DTA characterized the hybrid inorganic–organic nano composite. The dendrimeric and hyper-branched porous network structure, including branches of 5–15 nm in diameter was detected. The mechanism of polybranching and dendrimerization was proposed and discussed. It was coated on the surface of a metal mesh to study its hydrophilicity, through contact angle measurement, using oil and water separately. The material was also proved to be hydrophilic, due to its large number of carboxyl and hydroxyl groups. PC-A nanostructure was thermally stable up to 199 °C. Thermal degradation of the material led to the formation of gibbsite at about 550 °C, proving a reverse change of phase from boehmite to gibbsite. Thus, the PC-A, which was synthesized from BNs, finally produced gibbsite on burning.

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