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采用酶酸连续降解壳聚糖制备低分子量水溶性壳聚糖。首先确定了单因素降解壳聚糖的最佳技术参数:木瓜蛋白酶降解壳聚糖时最优条件为45℃、2h;醋酸降解壳聚糖时最优条件为30℃、4h;盐酸降解壳聚糖最优条件为90℃、8h;然后根据单因素降解壳聚糖最优条件确定了酶酸连续降解壳聚糖新工艺,并优化反应时间为7h。在相同条件下,酶酸连用方法最终降解产物的粘度低于单因素降解产物的粘度,产物表面性状有很大不同,分子量由降解前的33523.14下降到3134.11。 相似文献
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低聚壳聚糖制备及其生理活性进展 总被引:10,自引:0,他引:10
由壳聚糖降解制备的低聚壳聚糖具有许多独特的生理活性.本文在介绍低聚壳聚糖的生理活性的基础上,重点评述了酸降解法、氧化降解法、酶降解法以及组合降解工艺等各种制备方法的研究进展. 相似文献
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降解壳聚糖季铵盐是将降解壳聚糖的氨基通过引入基团转换成季铵盐或者把一个低分子季铵盐接到氨基上而得到的一类降解壳聚糖衍生物。降解壳聚糖季铵盐在亚麻织物染色中的应用研究表明其具有一定的助染作用。国外对壳聚糖季铵盐的合成已有报道,如1985年国外报道了碘化壳聚糖季铵盐的合成方法,但得到的碘化N-三甲基壳聚糖季铵盐是不溶于水的。 相似文献
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在简单均相体系下.研究了壳聚糖及丁二酸酐酰化壳聚糖在双氧水中的降解特性。采用鸟氏粘度计,利用一点法测量了降解过程中壳聚糖及丁二酸酐酰化壳聚糖的分子量,讨论了该体系下壳聚糖及丁二酸酐酰化壳聚糖的降解速率.通过红外光谱分析了双氧水对低分子量壳聚糖和低分子量丁二酸酐酰化壳聚糖结构的影响。结果表明.在该体系下·壳聚糖及丁二酸酐酰化壳聚糖的降解主要发生在反应开始后的2~3h内.此后降解产物的分子量逐渐趋于20000;相同条件下,丁二酸酐酰化壳聚糖的降解程度高于壳聚糖;红外光谱表明.采用该降解体系制备的降解产物主链结构基本没有发生变化。 相似文献
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将壳聚糖进行液态均相配合反应制得壳聚糖锰配合物,IR、元素分析及热分析等检测证实了壳聚糖锰配合物中配位键的存在,且显示壳聚糖锰配合物存在有利于壳聚糖高分子链断裂的弱势结构。以H2O2对壳聚糖.Mn(Ⅱ)配合物及壳聚糖进行氧化降解,考察降解过程中粘度的变化及降解产物分子量分布,在相同的降解条件下,壳聚糖锰配合物的降解速度明显高于壳聚糖,且降解产物分子量分布较壳聚糖直接降解窄。对壳聚糖锰配合物降解反应动力学研究表明壳聚糖锰配合物对H2O2分解不存在催化作用,其降解反应与壳聚糖的差异只与其结构有关。对降解产物进行脱金属处理,所得低聚壳聚糖含锰量为0。 相似文献
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在微波辐照下,采用NaNO2氧化降解壳聚糖,研究了反应时间、反应温度、 NaNO2用量等不同条件对壳聚糖解速率的影响情况。实验结果表明微波辅助能明显促进壳聚糖的降解,适当增加NaNO2用量和提高反应温度均能加快壳聚糖的氧化降解速率。 相似文献
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Quanyuan Cai Zhiming Gu Tingming Fu Yan Liu Hongchang Song Fengsheng Li 《Polymer Bulletin》2011,67(4):571-582
The kinetics of chitosan degradation by an electrochemical process was studied in this work. The order of degradation reaction
was determined according to the dependence of degradation rate constant on initial chitosan concentration. For electrochemical
degradation of chitosan, the apparent rate constant varied inversely with initial chitosan concentration, suggesting that
the degradation reaction was zeroth-order in chitosan concentration. The influence of experimental conditions on the degradation
rate constant was also investigated in detail. The degradation rate constant increased with current density, acetic acid concentration,
and temperature. The influence of temperature on the degradation rate was modeled using the Arrhenius equation and the activation
energy was determined to be 14.16 kJ/mol under the experimental conditions examined. The variation of sodium acetate concentrations
had a negligible influence on degradation rate of chitosan. 相似文献
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Chun‐Yan Ou Si‐Dong Li Lei Yang Cheng‐Peng Li Peng‐Zhi Hong Xiao‐Dong She 《Polymer International》2010,59(8):1110-1115
The thermal degradation of chitosan and chitosan–cupric ion compounds in air was studied using thermogravimetric and differential thermal analyses in the temperature range 30–600 °C. The impact of cupric ion on the thermo‐oxidative degradation of chitosan was investigated. Fourier transform infrared and X‐ray diffraction analyses were utilized to determine the microstructure of the chitosan–cupric ion compounds. Kinetic parameters such as activation energy, pre‐exponential factor, Gibbs energy, and enthalpy and entropy of activation were determined using the Coats–Redfern equation. The results show that the thermo‐oxidative degradation of chitosan and chitosan–cupric ion compounds is a two‐stage reaction. The impact of cupric ion on the thermo‐oxidative degradation of chitosan is significant, and all thermodynamic parameters indicate that the thermo‐oxidative degradation of chitosan and chitosan–cupric ion compounds is a non‐spontaneous process and proceeds via a mechanism involving nucleation and growth, with an Avrami–Erofeev function (A4) with the integral form [?ln(1 ? α)]4. Copyright © 2010 Society of Chemical Industry 相似文献
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The thermal degradation of metal complexes formed by chitosan with Cu(II), Ni(II), Co(II), and Hg(II), at different metal concentrations, was studied by thermogravimetric analysis in a nitrogen atmosphere over the temperature range 25–800°C. The results indicate that thermal degradation of chitosan and chitosan‐metal ion complexes could be of one or two‐stage reaction. In the thermal degradation of chitosan with metal complexes, the temperature of initial weight loss and the temperature of maximum weight loss rate decrease. Fourier transform infrared spectroscopy was used to probe the interaction of chitosan with metal ions. The bands of ? N? H, ? C?O, ? C? O? C? groups of chitosan are shifted or change their intensity in the presence of metal. These changes in the characteristic bands are taken as evidence of the influence of metal ions on the thermal stability of chitosan. Broido's method was employed to evaluate the activation energies as a function of the degree of degradation. The presence of metal ions provoked a decrease in the thermal stability of chitosan, which became more marked when the concentration of metal was increased. The dynamic study showed that the apparent activation energy values of the main stage of the thermal degradation of chitosan‐metal complexes decrease as the strength of the polymer‐metal interaction increases. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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利用热重分析(TGA)和差热分析(DTA)研究了壳聚糖及其铜离子混合物在氮气气氛和空气气氛中的热降解行为,探讨了气氛对壳聚糖及其铜离子混合物热降解的影响,并采用FTIR、X-射线衍射对壳聚糖铜离子混合物进行了表征.结果显示,壳聚糖及其铜离子混合物的热降解和热氧降解分三个阶段进行:第一阶段为材料失水,为吸热反应;第二阶段为主链脱乙酰和糖苷键的裂解,为放热反应;第三阶段为吡喃环的裂解和炭化残渣的分解,为放热反应.气氛对壳聚糖第一、第二阶段的降解影响较小,对第三阶段的降解影响较大. 相似文献