壳聚糖溶解行为及溶液特性的探究

Dissolution behavior and solution properties of chitosan

本实验主要测定了四种不同脱乙酰度、分子量的壳聚糖样品在浓度6%~12%,50℃下,定时滴加盐酸过程中溶液透光率、电导率、粘度和颗粒状态的变化,探索壳聚糖的溶解规律及溶液特性。结果表明:当盐酸浓度在0.23~0.39 mol/L时,壳聚糖浓度在6%~10%时,壳聚糖溶液透光率急剧上升;壳聚糖浓度越高,脱乙酰度越高,导致透光率急剧上升的起始盐酸浓度越高;分子量越小,加酸后,溶液最终透光率越高;随着酸的不断添加,壳聚糖溶液电导率先均匀小幅增加,盐酸超过一定浓度后增幅超过10 ms/cm,推测此时壳聚糖分子近乎完全质子化,壳聚糖脱乙酰度越高,溶液电导率大幅增加对应的盐酸浓度也越高;1#、2#、3#、4#壳聚糖溶液浓度为8%时,分别在盐酸浓度为0.29、0.29、0.34、0.34 mol/L时粘度最大,之后随加酸进行溶液粘度骤降;温度升高溶液粘度降低,但溶液粘度随盐酸浓度变化的规律不变;显微观察发现,随着加酸溶液中壳聚糖颗粒数显著减少,壳聚糖脱乙酰度越高,使颗粒全部崩解所需要的盐酸浓度越高,在颗粒全部崩解阶段溶液透光率、电导率剧烈变化,均显著升高。

The changes in transmittance, conductivity, viscosity and particle status of four kinds of chitosan solutions with different degree of deacetylation and molecular weight were mainly studied with different HCl and chitosan concentrations of 0-0.44 mol/L,6% - 12%, respectively, under 50℃ and the dissolution trends and solution properties of chitosan were investigaled.Resuhs showed that when the HCl and chitosan concentration was 0.23-0.39 mol/L,6%- 10% respectively, the transmittance of chitosan solution increased dramatically, the higher the chitosan concentration and degree of acetylation, the higher the HCl concentration at which transmittance began to increase sharply. After finishing adding HCl, the lower the molecular weight of chitosan, the higher the final transmittance of chitosan solution. The conductivity of chitosan solution increased at a small and even ratio when HCI concentration was low. After HC1 concentration was higher enough, the conductivity of solution rose at a ratio over 10 ms/cm, which indicated that chitosan was almost fully protonated.The higher the degree of deacetylation of ehitosan, the higher the HCl concentration at which conductivity of solution increase dramatically. 1#, 2#,3#,4# chitosan solution reached the maximum viscosity at concentration of HCl of 0.29 mol/L,0.29 mol/L,0.34 mol/L, 0.34 mol/L,respectively, then decreased significantly （p 〈 0.05 ）. Temperature increasing led to the decrease of solution vlscosity,but the effect of temperature on viscosity was not changed.Microscopy observation showed that the number of ehitosan particles decreased obviously with addition of hydrochloric acid. Chitosan with a higher degree of deacetylation fully disintegrated at a higher HC1 concentration.The transmittance and conductivity of solution increased obviously at the stage at which of ehitosan particles disintegrated fully.