Council of Scientific and Industrial Research (CSIR)-Central Leather Research Institute (CLRI), Chemical Physics Laboratory, Adyar, Chennai, India.
J Colloid Interface Sci. 2011 Aug 1;360(1):154-62. doi: 10.1016/j.jcis.2011.04.008. Epub 2011 Apr 16.
The present work was undertaken with a view to understand the influence of a model non-ionic tri-block copolymer PEO-PPO-PEO (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)) with molecular weight 5800 i.e., P123 [(EO)(20)-(PO)(70)-(EO)(20)] on the self-aggregation characteristics of the anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D(2)O) using NMR chemical shift, self-diffusion and nuclear spin-relaxation as suitable experimental probes. In addition, polymer diffusion has been monitored as a function of SDS concentration. The concentration-dependent chemical shift, diffusion data and relaxation data indicated the significant interaction of polymeric micelles with SDS monomers and micelles at lower and intermediate concentrations of SDS, whereas the weak interaction of the polymer with SDS micelles at higher concentrations of SDS. It has been observed that SDS starts aggregating on the polymer at a lower concentration i.e., critical aggregation concentration (cac=1.94 mM) compared to polymer-free situation, and the onset of secondary micelle concentration (C(2)=27.16 mM) points out the saturation of the 0.2 wt% polymer or free SDS monomers/micelles at higher concentrations of SDS. It has also been observed that the parameter cac is almost independent in the polymer concentrations of study. The TMS (tetramethylsilane) has been used as a solubilizate to measure the bound diffusion coefficient of SDS-polymer mixed system. The self-diffusion data were analyzed using two-site exchange model and the obtained information on aggregation dynamics was commensurate with that inferred from chemical shift and relaxation data. The information on slow motions of polymer-SDS system was also extracted using spin-spin and spin-lattice relaxation rate measurements. The relaxation data points out the disintegration of polymer network at higher concentrations of SDS. The present NMR investigations have been well corroborated by surface tension and conductivity measurements.
本工作旨在研究分子量为 5800 的模型非离子三嵌段共聚物 PEO-PPO-PEO（聚（环氧乙烷）-聚（环氧丙烷）-聚（环氧乙烷））对阴离子表面活性剂十二烷基硫酸钠（SDS）在水溶液（D（2）O）中自组装特性的影响，使用 NMR 化学位移、自扩散和核自旋弛豫作为合适的实验探针。此外，还监测了聚合物扩散作为 SDS 浓度的函数。浓度依赖性的化学位移、扩散数据和弛豫数据表明，在 SDS 的较低和中间浓度下，聚合物胶束与 SDS 单体和胶束之间存在显著的相互作用，而在 SDS 的较高浓度下，聚合物与 SDS 胶束之间存在较弱的相互作用。已经观察到 SDS 在较低浓度（即临界聚集浓度（cac=1.94 mM））下开始在聚合物上聚集，与无聚合物的情况相比，而二级胶束浓度（C（2）=27.16 mM）的出现表明在 SDS 的较高浓度下，0.2wt%的聚合物或游离 SDS 单体/胶束达到饱和。还观察到，在研究的聚合物浓度范围内，cac 参数几乎是独立的。TMS（四甲基硅烷）已被用作增溶剂来测量 SDS-聚合物混合体系的结合扩散系数。自扩散数据使用双位点交换模型进行分析，得到的聚集动力学信息与化学位移和弛豫数据推断的信息一致。还使用自旋-自旋和自旋-晶格弛豫率测量提取了聚合物-SDS 体系的慢运动信息。弛豫数据表明在 SDS 的较高浓度下聚合物网络的解体。本 NMR 研究得到了表面张力和电导率测量的很好验证。
