Characterization of a Dialdehyde Chitosan Generated by Periodate Oxidation

This article reports the oxidation of Chitosan by using periodate and the characterization of the dialdehyde chitosan (DAC) generated by the reaction. Oxidised chitosan were further characterised by FTIR analysis, 1HNMR and TGA. The morphological analyses of oxidized chitosan by SEM confirmed the non change of elongated and fibrous network of chitosan. FTIR and TGA show no significant change on chemical structure and thermal properties successively. 1H NMR study confirmed the presence of imines generated by the reaction between dialdehyde chitosan and amino groups of chitosan (spontaneous assembling)

Hybrid materials based on polyethylene and MCM-41 microparticles functionalized with silanes: catalytic aspects of in situ polymerization, crystalline features and mechanical properties

New nanocomposites based on polyethylene have been prepared by in situ polymerization of ethylene in presence of mesoporous MCM-41. The polymerization reactions were performed using a zirconocene catalyst either under homogenous conditions or supported onto mesoporous MCM-41 particles, which are synthesized and decorated post-synthesis with two silanes before polymerization in order to promote an enhanced interfacial adhesion. The existence of polyethylene chains able to crystallize within the mesoporous channels in the resulting nanocomposites is figured out from the small endothermic process, located at around 80 C, on heating calorimetric experiments, in addition to the main melting endotherm. These results indicate that polyethylene macrochains can grow up during polymerization either outside or inside the MCM-41 channels, these keeping their regular hexagonal arrangements. Mechanical response is observed to be dependent on the content in mesoporous MCM-41 and on the crystalline features of polyethylene. Accordingly, stiffness increases and deformability decreases in the nanocomposites as much as MCM-41 content is enlarged and polyethylene amount within channels is raised. Ultimate mechanical performance improves with MCM-41 incorporation without varying the final processing temperature