DERIVATIVES OF AMPHIPHILIC CATIONIC CHITOSAN: THERMAL CHARACTERIZATION

摘要

This work aims the synthesis and characterization of cationic amphiphilic chitosan derivatives with different molecular weights. The chitosan used in the reactions was obtained from the purification of commercial chitosan (QC). The average degree of deacetylation of chitosan purified (PQ) is 85%. The purified chitosan was depolymerized to obtain low molar weight polymers (QD21 and QD5), wherein the average viscosimetric molar weights of QP polymers, QD21 and QD5 certain was 66 000 g mol~(-1), 21 000 g mol~(-1) and 5 000 g mol~(-1), respectively. The partially depolymerized derivatives QD21 and QD5 were reacted with DEAE to obtain hydrophilic chitosan derivatives. The degrees of substitution with DEAE groups were determined by H-NMR and the values ??obtained were 40 and 49% for biopolymers QD21 and QD5, respectively. Then derivatives QD21-40DEAE and QD5-49DEAE were alkylated with aldehyde dodecyl and amphiphilic derivatives with different degrees of substitution by hydrophobic groups were obtained. The degrees of replacement by dodecyl groups to chitosan QD21-40DEAE were 6 and 18%. For the derivative containing 49% DEAE degrees of substitution by groups dodecyl were 6 and 17%. The success of obtaining the amphiphilic derivatives was indicated by H-NMR, addition FTIR-ATR. The polymers are also characterized by Thermogravimetric Analysis, and it was found that the thermal stability of the polymer is dependent on its molecular weight and the inserts of both hydrophilic and hydrophobic groups decrease as the polysaccharide degradation onset temperature. Result is in agreement with images obtained by SEM, showing that the substitution reactions with DEAE and dodecyl groups increased the porosity of the polymer, thereby facilitating the thermal degradation of chitosan derivatives.