Chemically modified chitosan with glyoxal in the absence of solvent

Full text: Chitosan is an animal-based polymer obtained from the alkaline deacetylation of chitin. Both show important biological effects, e.g. antimicrobial activity. Many methods have been proposed for obtaining structural derivatives of chitosan to promote cross-linking of the polymer chains of this biopolymer strategy that gives the modified chitosan different properties. The reaction of chitosan with glyoxal produces intramolecular cross-linking. In this work, chitosan was chemically modified by reaction with glyoxal in the absence of solvent. The pure chitosan (PP) and the modified chitosan with glyoxal (QG) were characterized by elemental analysis, FTIR, TG, and RMN ¹³C. The proportions of C, N and H calculated based on element analysis indicates that the material has been modified, due to the increase of percentage of carbon and decreasing percentage of nitrogen, since the glyoxal is composed by carbon, oxygen and hydrogen. The FTIR spectra of the cross-linked shows an increase in the intensity of the sharp peak at 1600 cm^-1 which may be due to the CN of the formed Schiff base between the remained free amino groups of chitosan and aldehyde groups of the cross-linker glyoxal. The major change of RMN ¹³C observed occurred in the formation of the imine bond, present in the region between 160 ppm. The results attained from the chemical characterization were compatible with the structural modifications carried out. Reference: [1] ZHAO, Z.; ZHENG, J.; WANG, High performance ultrafiltration membrane based on modified chitosan coating and electrospun nanofibrous PVDF scaffolds. Journal of Membrane Science, v. 394-395, p. 209-217, 2012. (author)