Surfactant head group and concentration influence on structure and dynamics of gellan gum hydrogels: Crossover from stretched to compressed exponential,Journal of Polymer Science

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Surfactant head group and concentration influence on structure and dynamics of gellan gum hydrogels: Crossover from stretched to compressed exponential
Journal of Polymer Science ( IF 3.9 ) Pub Date : 2021-07-09 , DOI: 10.1002/pol.20210326
K Mithra ₁ , Sidhartha S Jena ₁

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In the present study, we have investigated the effects of surfactant addition on the structure and dynamics of gellan gum hydrogels. A strong interaction is seen between gellan gum and oppositely charged cationic surfactant, hexadecyltrimethylammonium bromide (CTAB) whereas rather weak or minimal interactions are observed when either anionic surfactant, sodium dodecylsulfate (SDS), or nonionic surfactant, Triton X-100 is added to the system. The dynamics of the hydrogels was studied, using dynamic light scattering measurements and the heterodyne method was used for data evaluation. The correlation function of parent hydrogel was fitted with a stretched exponential function, while a single plus stretched exponential function was employed to study the dynamics of hydrogel with surfactants and the corresponding relaxation times were appropriately analyzed. An interesting crossover from stretched to compressed exponential was seen when CTAB was added beyond critical micellar concentration to the system, which was not evidenced for the other two surfactants. Ensemble averaged intensity was also analyzed and the general picture that emerges is that the oppositely charged surfactant has the strongest ability to form large associations as oppose to nonionic and like-charged surfactants. The rheological measurements were carried out to determine the elastic response of the gels over a wide range of frequencies. It was seen that the elastic modulus was dependent on both the surfactant concentration and type. Cationic surfactant increased the elastic modulus markedly as opposed to the nonionic and anionic surfactants. These results may have implications for the use of polymer surfactant systems as potential products.

中文翻译：

表面活性剂头基和浓度对结冷胶水凝胶结构和动力学的影响：从拉伸到压缩指数的交叉

在本研究中，我们研究了表面活性剂添加对结冷胶水凝胶结构和动力学的影响。在结冷胶和带相反电荷的阳离子表面活性剂十六烷基三甲基溴化铵 (CTAB) 之间观察到很强的相互作用，而当阴离子表面活性剂十二烷基硫酸钠 (SDS) 或非离子表面活性剂 Triton X-100 添加到系统。研究了水凝胶的动力学，使用动态光散射测量，外差法用于数据评估。母体水凝胶的相关函数与拉伸指数函数拟合，同时采用单加拉伸指数函数来研究具有表面活性剂的水凝胶的动力学，并适当地分析了相应的弛豫时间。当 CTAB 添加到系统中超过临界胶束浓度时，可以看到从拉伸指数到压缩指数的有趣交叉，而其他两种表面活性剂没有证明这一点。还分析了整体平均强度，得出的一般情况是，与非离子和同电荷表面活性剂相反，带相反电荷的表面活性剂具有最强的形成大缔合的能力。进行流变测量以确定凝胶在很宽的频率范围内的弹性响应。可以看出，弹性模量取决于表面活性剂的浓度和类型。与非离子和阴离子表面活性剂相比，阳离子表面活性剂显着增加了弹性模量。这些结果可能对使用聚合物表面活性剂系统作为潜在产品有影响。

更新日期：2021-09-01

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