Síntese e caracterização de quitosana como suporte para o desenvolvimento de polímeros híbridos contendo níquel(II)

Abstract

Chitin and chitosan are obtained by the alkaline hydrolysis process. Chitosan is a biopolymer that can be functionalized by immobilizing binders with chelating properties that can modify its physical, chemical and biological properties. This work has objectives as synthesis of chitosan from shrimp shells and modifies its structure using organic and inorganic compounds to obtain unpublished materials. The support of triazenes 1-oxide and their complexes in chitosan is unprecedented; because of this these compounds were chosen for the immobilization reactions. Chitosan was obtained by complete factorial planning in three stages: demineralization, deproteinization and deacetylation. The best responses were: demineralization (84.3 %), deproteinization (98.30 %), deacetylation (66.1%) and the medium molecular mass was 372 KDa. Commercial (Sigma Aldrich®) and synthesized chitosan were modified by immobilization of 1-methyl-3- (p-carboxyphenyl) triazene 1-oxide (1) and bis [1-methyl-3- (p-carboxyphenyl) triazene 1-oxide] NiII (2). This support process results in organic materials (3a) and (3b) and hybrid materials (4a) and (4b), respectively. The results obtained from infrared spectroscopy (FTIR) showed the [N=N] band of compound (1) at 1420 cm-1 and 1427 cm-1 in spectrum of compounds (3a) and (3b), respectively. Chitosan bands [C-O-C] were observed in 1102 cm-1 , 1024 cm-1 for (3a) and 1097, 1048 cm-1 for (3b). Change in the band [O-H] in compounds (3a) and (3b) compared to compound (1) was observed due to the stretching vibrations of the hydrogen bonds (-NHO- ), this evidence shows the presence of interactions between the carboxylate group (-COO- ) of compound (1) and the protonated amino group (NH3 + ) of chitosan. The band [NNN] observed at 1394 cm-1 in the spectrum of the triazenide complex (2) showed a shift in the compounds (4a) and (4b) observed at 1378 and 1396 cm-1 , respectively, showing the binding of compound (2) to chitosan. The bands [CO-C], characteristic of chitosan were observed in 1079, 1042 cm-1 for (4a) and 1072 cm-1 for (4b). Differential scanning calorimetry (DSC) evidenced the loss of thermal stability of compounds (3a) and (3b) as compared to chitosan. Exothermic peaks have been identified, suggesting the presence of compound (1) (214.47 ºC) in (3a) 189.50 ºC and (3b) 194.93 ºC. In addition, exothermic peaks were identified at 242.37 ºC (4a) and 237.87 ºC (4b), suggesting the presence of compound (2) (260.11 ºC) in the structure of these hybrid materials. Scanning electron microscopy (SEM) and dispersive energy spectroscopy (EDS) showed morphology and qualitative analysis of compound (1) and of unpublished compounds (2), (3a), (3b), (4a) and (4b).