Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway.
J Phys Chem B. 2010 May 20;114(19):6273-80. doi: 10.1021/jp100333f.
Interactions between the anionic surfactant sodium dodecyl sulfate (SDS) and hydroxyethylcellulose (HEC) or its hydrophobically modified analogue (HM-HEC) have been studied over an extended temperature region with the aid of turbidimetry, small-angle neutron scattering (SANS), and shear viscosimetry. Anomalous viscosity enhancements were observed for semidilute HEC/SDS and HM-HEC/SDS solutions at high SDS concentrations at temperatures far below the Krafft point for aqueous solutions of SDS. From the Arrhenius-Frenkel-Eyring (AFE) plots of the temperature dependence of the zero-shear viscosity, the activation energy of chain disengagement (DeltaE(vis)) was found to be on the order of 40 kJ mol(-1) for the HEC/SDS mixtures, whereas for the HM-HEC/SDS system, much higher values of DeltaE(vis) (up to 141 kJ mol(-1)) were reported, and the activation energy increased with an increasing level of SDS addition. Break points in the AFE plots were observed for both the HEC/SDS and HM-HEC/SDS systems at low temperatures and high SDS concentrations. Time evolutions of both the turbidity and the shear viscosity were monitored after quenching of the temperature from 25 to 1 degrees C. The turbidity results revealed in general a less pronounced transition for the HEC/SDS and HM-HEC/SDS systems than for the corresponding polymer-free SDS/water solutions. In the course of time, a significant viscosity enhancement was found for the HEC/SDS system at high levels of SDS addition, and a much stronger viscosification was observed for the HM-HEC/SDS system at the highest surfactant concentration. The overall results suggest that hydrated SDS aggregates act as cross-linkers of the network and generate the substantial viscosification of the systems at low temperature and high levels of SDS addition. For the HM-HEC/SDS system, further strengthening of the network occurs because of the contribution from hydrophobic interactions. The SANS data on HEC/SDS mixtures reveal that some structural reorganization takes place at low temperatures in the presence of high SDS concentrations, and this is ascribed to enhanced polymer-SDS interactions and the formation of clusters that strengthened the cross-links of the network.
阴离子表面活性剂十二烷基硫酸钠（SDS）与羟乙基纤维素（HEC）或其疏水改性类似物（HM-HEC）之间的相互作用已在较宽的温度范围内借助浊度法、小角中子散射（SANS）和剪切粘度测量进行了研究。在远远低于 SDS 水溶液的克拉夫特点的温度下，在高 SDS 浓度下，半浓 HEC/SDS 和 HM-HEC/SDS 溶液表现出异常的粘度增强。从零剪切粘度随温度的阿雷尼乌斯-弗伦克尔-埃林（AFE）图可以看出，HEC/SDS 混合物的链脱离活化能（DeltaE(vis)）约为 40 kJ mol(-1)，而对于 HM-HEC/SDS 体系，报道的 DeltaE(vis) 值要高得多（高达 141 kJ mol(-1)），并且活化能随着 SDS 添加量的增加而增加。在这两种 HEC/SDS 和 HM-HEC/SDS 体系中，在低温和高 SDS 浓度下，AFE 图中都观察到了断点。在从 25 到 1 摄氏度的温度淬火后，监测了浊度和剪切粘度的时间演化。总的来说，与相应的无聚合物 SDS/水溶液相比，HEC/SDS 和 HM-HEC/SDS 体系的浊度转变不那么明显。随着时间的推移，在高 SDS 浓度下，HEC/SDS 体系的粘度显著增强，而在最高表面活性剂浓度下，HM-HEC/SDS 体系的粘度增强更为强烈。总体结果表明，水合 SDS 聚集体充当网络的交联剂，并在低温和高 SDS 浓度下使体系产生显著的增稠作用。对于 HM-HEC/SDS 体系，由于疏水相互作用的贡献，网络得到进一步加强。HEC/SDS 混合物的 SANS 数据表明，在高 SDS 浓度存在的情况下，在低温下会发生一些结构重组，这归因于增强的聚合物-SDS 相互作用和形成的团簇，这些团簇加强了网络的交联。
