Thermal gelation of chitosan in an aqueous alkali-urea solution
Thermal gelation of chitosan in an aqueous alkali-urea solution
复制标题
壳聚糖在碱-尿素水溶液中的热凝胶化
DOI：
10.1039/c4sm01336k
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发表时间：
2014-01-01
期刊：
影响因子：
3.4
通讯作者：
Zhang, Yongjun
中科院分区：
文献类型：
--
作者：
Li, Chong;Han, Qiuyan;Zhang, Yongjun
壳聚糖可以很容易地溶解在预冷的碱-尿素水溶液中，这是一种以前被开发用来溶解纤维素的溶剂。加热后，产生的溶液迅速变成凝胶。用流变学方法研究了壳聚糖溶液的热胶化过程。最初，使用温度斜坡测试来确定凝胶温度（t -凝胶）。结果表明，t -凝胶不随壳聚糖浓度的变化而变化。原位形成的凝胶在冷却时液化，但液化温度（T-liq）明显低于T-gel，表明冷却过程中存在较大的滞后。T-liq随聚合物浓度的增加而降低。然后通过等温固化研究了热凝胶动力学。溶液凝胶不仅在温度斜坡试验中确定的高于t -凝胶的温度下固化，而且在远低于t -凝胶的温度下固化，前提是溶液在该温度下固化的时间足够长。溶液在较高的温度下固化会更快地变成凝胶。当在相同温度下固化时，浓度越高的溶液凝胶化速度越快。壳聚糖溶液热凝胶反应的表观活化能约为200 kJ mol（-1）。将原位形成的壳聚糖在水中反复浸泡，得到了纯壳聚糖的物理凝胶。初步试验表明，这种新型凝胶具有很高的生物相容性。
Chitosan can readily dissolve in a precooled aqueous alkali-urea solution, a solvent that has previously been developed to dissolve cellulose. Upon heating, the resulting solutions quickly become a gel. The thermal gelling of the chitosan solutions was studied by rheology. Initially, a temperature ramp test was used to determine the gelation temperatures (T-gel). It was found that T-gel does not significantly change with chitosan concentration. The in situ formed gels liquefy on cooling, but the liquefication temperature (T-liq) is considerably lower than T-gel, indicating a large hysteresis in the cooling process. In addition, T-liq decreases with increasing polymer concentration. The kinetics of thermal gelation was then studied by isothermal curing. The solution gels were cured not only at temperatures above the T-gel, which was determined in the temperature ramp test, but also at temperatures far below the T-gel, provided that the solution is cured at the temperature for a long enough time. The solutions become gel faster when cured at higher temperatures. When cured at the same temperature, higher concentration solutions become gel faster. The apparent activation energy for the thermal gelation of the chitosan solutions was determined to be similar to 200 kJ mol(-1). Physical gels of pure chitosan were obtained by repeated soaking the in situ formed gels in water. Preliminary test shows that new gels are highly biocompatible.