十二烷基磺酸钠对κ-卡拉胶溶胶-凝胶转变的影响

研究了阴离子表面活性剂十二烷基磺酸钠(sodium dodecyl sulfonate, SDSN)对同荷聚阴离子多糖κ-卡拉胶(κ-CAR)溶胶-凝胶转变的影响. 通过不同浓度的SDSN加入前后对κ-CAR溶液的流变行为和热行为的比较发现, SDSN随浓度不同基本以两种方式影响κ-CAR的溶胶-凝胶转变, 低浓度时(c＜5 mmol•L－1) SDSN对κ-CAR的溶胶-凝胶转变影响很小, 仅有轻微的促进作用, 使凝胶的起始温度和转变温度略向高温方向移动; 而当c＞5 mmol•L－1时, SDSN显著影响κ-CAR的溶胶-凝胶转变, 使转变温度向低温方向移动, 凝胶形成变得困难. 同时发现, SDSN的浓度大于其临界胶束浓度(CMC)时, 伴随κ-CAR的凝胶过程形成类似SDSN低温结晶的有序结构. 进一步利用生物染料亚甲基兰(MB)为探针, 通过测定κ-CAR-MB体系的UV-Vis光谱, 探讨了阴离子表面活性剂SDSN与聚阴离子κ-CAR相互作用的机理可能为同种电荷之间的静电排斥作用、对K＋的竞争以及疏水作用.

Effects of Sodium Dodecyl Sulfonate on the Sol-gel Transition of K-Carrageenan

The effects of anionic surfactant sodium dodecyl sulfonate (SDSN) on the sol-gel transition of κ-carrageenan (κ-CAR), an anionic polysaccharide, have been investigated by different techniques including rheology, differential scanning calorimetry (DSC) and UV-Vis spectrometry. It has been found that, SDSN, at low concentrations (cSDSN＜5 mmol•L－1), slightly promoted the gelation of κ-CAR due to a weak salt-out effect, whereas at higher concentrations (c＞5 mmol•L－1), SDSN not only obviously decreased the sol-gel transition temperature of κ-CAR, but also formed a new ordered structure in the gel matrix of κ-CAR. The patterns of interactions between κ-CAR and SDSN were discussed. And a mechanism of cooperative interactions of electrostatic repulsion, competition for K＋and hydrophobic interaction has been proposed to interpret the experimental results.