氨基葡萄糖分子上羧基含量对壳聚糖性能影响

目的 利用漆酶-TEMPO（TEMPO为2,2,6,6-四甲基哌啶-1-氧基的简称）体系氧化低聚壳聚糖,探究氨基葡萄糖分子上引入的羧基含量对壳聚糖性能的影响,以期壳聚糖在包装方面的应用能够更为广泛。方法 通过高效离子色谱（HPIC）检测样品的钠离子含量表征样品的羧基含量,通过检测样品的吸湿保湿性、抗氧化性能表征壳聚糖物理化学性能的改善程度。结果 壳聚糖分子上引入羧基有利于改善其吸湿、保湿性能,氧化产物在饱和碳酸钾与饱和硫酸铵溶液中60 h后吸湿率最高达63.0%, 18.4%,保湿率为5.7%,而当氧化程度超过45.31%时,氧化产物的吸湿、保湿性能保持不变。结论 TEMPO添加量越多,氧化产物的羧基含量越高。引入的羧基基团能够改善壳聚糖氧化产物的吸湿、保湿性能,而增加氨基葡萄糖分子上的羧基含量,会提高壳聚糖的抗氧化性能。这些性能的提高对壳聚糖在包装材料的应用具有长远意义。     

Effect of carboxyl content on the physicochemical properties and intramolecular water distribution of 6-carboxyl chitooligomer prepared by laccase-TEMPO

6-carboxyl chitooligomer was prepared by degradation of chitosan with H₂O₂ followed by catalytic oxidation in the laccase-2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) system. The TEMPO was used as a single variable to alter the content of introduced carboxyl groups. The resulting oxidation products were analyzed by ion chromatography, scanning electron microscopy, and ¹H low-field NMR. Moisture absorption-retention ability, antioxidation, and thermal stability also were characterized. The results showed that the carboxyl content in the molecules increased with increasing TEMPO. With the addition of 8% TEMPO (mass fraction relative to chitooligomers), the carboxyl content and the oxidation degree of the product reached 4.90 mmol/g and 96.53%, respectively. Under these conditions, it also had the highest ABTS radical cation scavenging ability of 85.47% and improved thermal stability. When the amount of TEMPO was reduced to 2%, the oxidation product had a degree of oxidation of ~50% and showed a unique molecular structure and supreme moisture absorption-retention ability. A higher associated water content was observed inside the molecules where more bound water was locked in the process of moisture absorption. Furthermore, the physicochemical properties of 6-carboxyl chitooligomer were much higher than chitooligomer and oligomeric sodium hyaluronate (HA-Oligo). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47509.