Síntese e caracterização de quitosana e quitosana triazenídica: filmes e aplicações

Abstract

Chitin is the second most abundant biopolymer after cellulose and is present in the exoskeleton of crustaceans, being the raw material in the synthesis of chitosan. The present study has as one of its objectives to produce chitosan, from chitin extracted from pink shrimp shells from the Z-3 colony, Pelotas/RS, for the development of new films through the incorporation of new azo compounds, synthesized by diazotization (compounds C-01 and C-02). The chitin extraction processes by demineralization (DM) and deproteinization (DP) were standardized for the sample in question. The synthesis of chitosan was evaluated by traditional heating with reflux methodology and by ultrasound and microwave radiation. The steps of obtaining chitosan (DS) were evaluated through the analysis of solid samples: particle size, moisture and ash gravimetry, total nitrogen, infrared spectroscopy (FT-IR), thermogravimetry (TGA/DTG), microscopy of atomic force (AFM) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD). Chitosan (DS) samples synthesized using different methodologies were characterized in comparison to a commercially obtained chitosan sample (COM). The average degree of deacetylation (𝐺𝐷 ̅̅̅̅ ) was determined by potentiometric titration and the viscosimetric molar mass obtained by intrinsic viscosity analysis. The chitosan obtained by the use of microwaves stood out among the other samples for resulting in chitosan with a high degree of deacetylation (82.77%) and high viscosimetric molar mass (182.5 – 203.6 kDa), in synthesis by making use of shorter deacetylation time and lower energy expenditure. The compounds C-01 and C-02 were characterized by melting point, FTIV, MEV, EDS, TGA/DTA, as well as the films originated by their incorporation in

chitosan, as well as the films of pure chitosan and those with the addition of 0.005

molL-1 and 0.05 molL-1 copper(II) and cobalt(II) salts were characterized by: DRX, AFM, SEM, EDS, FT-IV, UV-Vis, TGA/DTA and dynamic mechanical analysis (AMD). The antifungal potential of acidic solutions (0.25%) of compounds C-01 and C-02, as well as synthesized chitosan samples (DS9h, DS MICRO , DS ULTRA ) and commercial (DS COM ), of filmogenic solutions of pure chitosan F- COM and F-DS 9h and those with the incorporation of C-01 and C-02 (F-COM/C-01 and F-DS 9h /C-02), was investigated in vitro against the fungus Colletotrichum gloeosporioides causing anthracnose in guava trees and proved the antifungal action known for chitosan, however the incorporation of C-01 and C-02 did not improve the activity of the films, on the contrary; the increase in nitrogen concentration encouraged fungal growth. The films F-COM, F-DS 9h , FCOM/C-01

and F-DS 9h /C-02 were evaluated as adsorbents of Cu(II) and Co(II) ions in aqueous medium, as a function of contact time .The adsorption capacity of these ions until equilibrium was determined. The best results in Cu(II) removal were: 48.13% for F-COM/C-01. The same films without metallic cations were evaluated in catalytic reactions of Suzuki-Miyaura coupling and initially showed to be promising for aiding catalysis performed by palladium. Finally, the syntheses, characterizations and evaluations carried out in this work proved to be adequate for the synthesis of chitosan using microwave radiation and in a green way by reusing waste, as well as promising for the synthesis of new films with diversified applications by the incorporation of triazenide chitosan.