微波间歇法快速制备高粘均分子量和高脱乙酰度的壳聚糖

使用微波间歇法可快速制备高脱乙酰度和高粘均分子量的壳聚糖. 单因素实验确定的工艺条件为微波功率800 W,将45%(w)的氢氧化钠溶液与250~380 mm的20 g甲壳素粉以8:1的体积比混合,在100℃下反应10 min,洗涤、微波干燥后在相同条件下再反应1次,共20 min,可制得脱乙酰度为94.5%、粘均分子量1.48×106的白色壳聚糖粉末. 其他制备条件相同,使用电加热法间歇处理甲壳素粉3次,反应共5 h,可以得到脱乙酰度为96.2%、粘均分子量为3.8×105的褐色壳聚糖粉末. 微波间歇法所制壳聚糖的结晶度高,内部有规整的有序结构,用它制备的膜致密,性能优于用电加热法所制壳聚糖制备的膜.     

蜚蠊壳聚糖的制备研究

以蜚蠊壳为原料用微波法制备甲壳素和壳聚糖 ,用过氧化氢于适当条件下脱色 ,所得甲壳素为白色片状 ,脱乙酰度大于 75 % ,收率 14 .7% ;继而用微波加热法制备壳聚糖 ,产物粘均分子量约 65 2 0 0 0 ,收率 79%。     

壳聚糖的微波干燥行为的研究

本文对壳聚糖在微波和烘箱技术条件下的干燥行为进行了研究。并对其脱乙酰度、粘度、分子量及红外光谱进行了测定。结果表明，用微波干燥处理壳聚糖所用的时间是用烘箱处理所需要的十分之一；而其脱乙酰度、粘度、分子量及红外光谱在两种条件下测得的结果几乎一致。实验还发现，在相同条件下，由虾壳制得的壳聚糖，其分子量和粘度都大于由蟹壳制得的产品。     

止血性壳聚糖的制备及其凝血效果的研究

在温和均相条件下,对较高脱乙酰度的壳聚糖进行乙酰化,制备不同脱乙酰度的壳聚糖;测试不同脱乙酰度和分子量的壳聚糖醋酸溶液的凝血效果。中药—壳聚糖复合止血材料的制备及其止血功能的研究。     

微波技术提取高脱乙酰度高黏度壳聚糖的实验研究

壳聚糖作为一种具有独特性能的天然高分子生物材料，其应用越来越广泛，并且对壳聚糖品质的要求也越来越高。高脱乙酰度和高黏度是壳聚糖的二个重要质量指标，传统制备工艺中，通过提高反应温度和延长反应时间，能得到高脱乙酰度的壳聚糖产品，但由于过长的反应时间使黏度大大降低。本文采用微波技术和传统工艺相结合，通过正交试验确定了从虾壳中提取高脱乙酰度高黏度壳聚糖的较优工艺条件。     

高脱乙酰度壳聚糖的制备及结构与性能研究

本文系统地研究了从虾壳制备高脱乙酰度、高分子量壳聚糖的方法。在一定条件下可得到脱乙酰度达97％,分子量达5×10~5左右的壳聚糖。用IR、NMR、DTA、TGA等分析技术对壳聚糖的结构与性能进行了研究。     

微波法制备壳聚糖絮凝剂的研究

以虾壳作为原料制得甲壳素后,用NaOH溶液浸润然后在微波作用脱去乙酰基和蛋白质制备壳聚糖;研究了影响壳聚糖脱乙酰度及粘均分子质量的因素;选择c（NaOH）=45%～50%,微波功率400 W,一次微波法反应时间10 min,可得脱乙酰度75%、分子质量（3.5～4） 万的壳聚糖;二次微波法每次反应时间分别为5 min,可得脱乙酰度90%的壳聚糖;与传统方法相比,缩短了反应时间,节约了能耗;将实验制得的壳聚糖作为絮凝剂用于含磷废水,絮凝效果明显,除磷率可达90%.     

低分子量壳聚糖的制备

利用H2O2的强氧化性制备低分子量分布的壳聚糖是将虾皮用HC l浸泡去除碳酸钙盐;再用稀碱除去蛋白质得甲壳素;然后浓碱在50℃与其反应,并控制反应时间,分别制备出脱乙酰度为85%,93%,99%的壳聚糖,最后用H2O2氧化不同脱乙酰化壳聚糖,得到不同低分子量的壳聚糖。其中,脱乙酰度为85%壳聚糖用不同浓度的H2O2降解,得到了4.7×105,3.5×105,2.5×105,1.2×105,8×105等5个不同分子量段的壳聚糖产品。H2O2浓度越大,降解所得壳聚糖的分子量就越小。     

高脱乙酰度壳聚糖的制备

以甲壳素为原料,以异丁醇为溶剂,氢氧化钠为亲核试剂,探讨了一种制备高脱乙酰度壳聚糖的新方法.研究了投料比、反应温度、反应时间、反应方法等对脱乙酰度的影响.结果表明,在反应温度为110℃,反应时间2.5h,壳聚糖∶NaOH∶醇=1∶5∶12(质量比)条件下制得脱乙酰度为93.2%的壳聚糖,而传统水溶剂脱乙酰度小于50%.另外间歇法处理样品可以在较短的时间里制备出脱乙酰度较高的壳聚糖,并用红外谱图对壳聚糖进行了表征.     

水溶性壳聚糖的制备及其应用研究进展

由于壳聚糖的结晶性.它只能溶于一些稀的无机酸或有机酸,不能直接溶于水中.文章介绍了几种水溶性壳聚糖的制备方法-控制壳聚糖的脱乙酰度、降低分子量和化学修饰,以及水溶性壳聚糖在医药、食品、化妆品等方面的应用进展.     

微波辐射制备壳聚糖

用质量分数34％的NaOH在微波辐射下对甲壳素进行非均相脱乙酰以快速制备壳聚糖，并测定了不同条件下制得的壳聚糖的相对分子质量和脱乙酰度，该反应时间短，重复性好，产品质量易控制。     

壳聚糖降解探索

本文着重讨论了壳聚糖的主要降解方法及使用氧化降解法制备低聚壳聚糖的方法,采用正交设计,探讨降解条件对产物脱乙酰度、特性粘度等的影响。     

Study of the influence of processing parameters on the production of carboxymethylchitin

Carboxymethylchitin was prepared at different reaction temperatures and from alkali chitin with different concentrations of alkali. Properties of the product were studied. Alkali chitin were prepared using freshly prepared sodium hydroxide of 45, 50, 55, 60 and 65% (w/w) concentration and carboxymethylated using monochloroacetic acid at controlled (35-40 °C) and uncontrolled (30-80 °C) temperature conditions. Molecular weight, viscosity, degree of deacetylation, etc. of the resultant product, i.e. carboxymethylchitin were determined. It was found that the reaction temperature has a profound influence on the property of the product than alkali concentration. A hygroscopic and completely water-soluble product was formed. Optimum conditions for the production of carboxymethylchitin were found to be 60% NaOH concentration and at 35-40 °C reaction temperature. At these conditions, it was obtained with a molecular weight of 4.11×10⁶ Da, viscosity 1926 cP and degree of deacetylation 45.02%.     

Hypocholesterolemic action of chitosans with different viscosity in rats

The relationship between hypocholesterolemic efficacy and average molecular weight of chitosan was studied in rats fed a cholesterol-enriched (0.5%) diet. Several chitosan preparations with a comparable degree of deacetylation but differing widely in average molecular weight, as demonstrated by viscosity, almost completely prevented the rise of serum cholesterol at the 5% dietary level. At the 2% level, chitosans with viscosities at both extremes exerted a comparable cholesterol-lowering action. The glucosamine oligomer composed mainly of three to five aminosugar residues was not effective. The results indicate that the hypocholesterolemic action of chitosans is independent of their molecular weight within the tested viscosity range.     

Highly deacetylated chitosan and its properties

A preparative method has been established for obtaining chitosan products which have a desired degree of deacetylation of up to virtually 100%. Effective deacetylation was attained by intermitently washing the intermediate product in water two or more times during the alkali treatment. The weight average molecular weight (M?_w) of the product, which was measured by gel permeation liquid chromatography, was about 5 × 10⁵ at the highest deacetylation of nearly 100%, and the degradation of the molecular chain was not so significant. Tensile strength of the wet film increased markedly with increasing degree of deacetylation, while the dry film did not show a corresponding significant increase of the tensile strength. In the infrared spectra of chitosan film new sharp bands appeared especially at the high degree of deacetylation. This was attributed to increased “crystallization” brought about by high deacetylation.     

Acid Hydrolysis of Chitosan to Oligomers Using Hydrochloric Acid

The natural polymer chitosan is widely used for medical and drug delivery applications. Low molecular weight chitosan (LMWC) has superior properties compared to high molecular weight chitosan (HMWC), which open new applications of LMWC, especially in the cosmetics, food, and pharmaceutical industries. LMWC is often produced from HMWC by acid, enzymatic, or oxidative hydrolysis. Industrially, hydrolysis with dilute HCl is preferred, since it is simple, practical, and gives a high yield. In this study 2M HCl was used to prepare LMWC. A high average depolymerization yield of 87% was obtained. The LMWCs were characterized by FTIR spectroscopy, and the molecular weight and degree of deacetylation were determined. The prepared LMWCs are fully deacetylated, and their production by this method is reproducible.     

Effect of molecular weight and degree of deacetylation of chitosan on urea adsorption properties of copper chitosan

Copper chitosan complexes prepared by different specifications of chitosan and copper sulfate were used as urea sorbents. Experimental results showed that the adsorption capacity for urea of copper chitosan increased with an increasing degree of deacetylation and decreasing molecular weight of chitosan. The urea adsorption capacity of copper chitosan was 120.0 mg/g, when 1.0 g of copper chitosan was admitted to 100 mL of a 1300 mg/mL (pH 6.0) urea solution, with chitosan degree of deacetylation of 84.3% and viscosity molecular weight of 6.5 × 10⁵, at 37°C for 8 h. No elution of the copper from the copper chitosan could be detected under the optimal conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1520–1523, 2003     

Influence of chitosan characteristics on coagulation and flocculation of organic suspensions

Several samples of chitosan with different degrees of deacetylation and of different molecular weights were tested for the coagulation–flocculation of organic suspensions. Organic suspensions were prepared by mixing mushroom powder with tap water. Experiments were carried out at pH 5, pH 7, and pH 9. Because decreasing the pH reduced the amount of chitosan required to reach the required turbidity, at pH 9, a high concentration of chitosan was required to achieve the required treatment levels, whereas the difference was less significant between pH 7 and pH 5 (the required concentration of chitosan was halved). Though viscosity, correlated to the molecular weight of chitosan, affected treatment performance, its influence on the efficiency of coagulation–flocculation could be substantially reduced by slightly increasing the concentration of the polymer. This is of importance in the processing of industrial effluents: the aging of a chitosan solution, which may cause partial depolymerization, and loss of viscosity, will have a limited impact on process efficiency. The degree of deacetylation also has a limited effect on treatment performance, especially when the degree of deacetylation exceeds 90%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2070–2079, 2005