Functionalization and characterization of new chitosan derivatives obtained by 1,3-dipolar cycloaddition reaction (CuAAC)

Chitosan is an important natural polymer in research due to its solubility in aqueous acidic solutions and its excellent properties, such as biodegradability, biocompatibility, bioactivity and non-toxicity. Copper-catalyzed 1,3-dipolar azide-alkyne cycloaddition reactions are used to obtain functionalized chitosan derivatives called 1,2,3-triazoles, which have a potential use as food coatings. From shrimp exoskeletons, chitosan was obtained with a yield of 24.66 %, a solubility of 84.11 %, a degree of deacetylation of 90.94% and a molecular weight of 352.28 kDa. From different terminales alkynes and by microwave-assisted 1,3-dipolar cycloaddition reaction (CuAAC), derivatives with shades varying between green-yellow, red-brown with high yields between [79.72 - 88.04] % were obtained. Films were elaborated from the derivatives and PVA which presented tensile strength values in a range between [65.21 - 94.17] MPa, an elongation at break varying between 31.33 % to 55.30 %. Thicknesses between [0.033-0.043] mm. They presented a higher thermal stability than chitosan with a decomposition range between [288.74 - 322.84] ºC, values obtained from differential scanning calorimetry tests. They possess a water vapor permeability between [2.28x10^-8 - 1.21x10^-7] (g/s.m.Pa). The derivatives obtained from microwave-assisted 1,3-dipolar cycloaddition reactions when applied in the manufacture of films possess improved mechanical properties, homogeneous thicknesses, low porous surfaces and good barrier properties, these characteristics would allow the formulation of food coatings.