Chitin Nanocrystals Prepared by TEMPO-Mediated Oxidation of alpha-Chitin

摘要

Chitin nanocrystals dispersed in water were successfully prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl radical(TEMPO)mediated oxidation of a-chitin in water at pH 10 under specific conditions,followed by ultrasonic treatment.When the amount of NaClO added as co-oxidant in the oxidation was 5.0 mmol/g of chitin,the weight percentage of the water-insoluble fraction in the TEMPO-oxidized chitin was 90%,and its carboxylate content reached 0.48 mmol/g.Since the TEMPO-oxidized chitin thus prepared had a crystallinity as high as that of the original a-chitin,the C6 carboxylate groups formed by TEMPO-mediated oxidation can be regarded as being present only on the chitin crystallite surfaces.No N-deacetylation occurred on the TEMPO-oxidized chitins.When the TEMPO-oxidized chitin was subjected to ultrasonic treatment in water,mostly individualized chitin nanocrystals were obtained,and the average nanocrystal length and width were 340 and 8 nm,respectively.