Synthesis of the N-butyl chitosan under microwave irradiation

High molecular weight chitosan was alkalized under microwave first and then the alkalized chitosan reacted with butyl bromide to synthesize N-butyl chitosan with high molecular weight and high degree of substitution(DS).The effects of alkalization method,alkalization and alkylation reaction temperature,reaction time of alkylation,and the ratio of reactant on the DS of N-butyl chitosan were investigated in detail,and the suitable reaction conditions were obtained as follows:n(sodium hydroxide)∶n(chitosan)=4∶1,viscosity-average molecular weight of chitosanis 1.49×106,microwave reaction alkalization temperature 60 ℃,reaction time 1 h,n(butyl bromide)∶n(alkalized chitosan)=1.4∶1,alkylation reaction temperature 80 ℃,alkalization reaction time 4 h.Under the above conditions,the molecular weight of N-butyl chitosan was 1.48×106 and the DS was up to 78.5%.The structure of alkalized chitosan was confirmed by SEM,the results indicated that the stereoregularity and the inter hydrogen bonds were destroyed.The structure of N-butyl chitosan was characterized by XRD and FT-IR.