Chakraborty Tanushree, Chakraborty Indranil, Ghosh Soumen
Centre for Surface Science, Department of Chemistry, Jadavpur University, Kolkata-700 032, India.
Langmuir. 2006 Nov 21;22(24):9905-13. doi: 10.1021/la0621214.
Interaction between polymer and surfactant bearing opposite charges is much more complex from a physicochemical point of view as compared to interaction between ionic surfactant and nonionic polymer. Electrostatic and hydrophobic interactions interplay in the former, whereas the hydrophobic effect is the prevailing factor in the latter. We have studied the interaction between a water-soluble polyanion, sodium salt of carboxymethylcellulose (NaCMC), with a cationic amphiphile, CTAB, in aqueous medium. There were manifold discrepancies with the reported works in NaCMC-alkyltrimethylammonium bromide, which is assumed to be an effect of difference in degree of substitution, which in turn affects the charge density of the polymer chain. We have noticed that the bulk complexation and interfacial interaction driven by electrostatic forces operate side by side. Thereafter, there is a wrapping process by the polyanion to the polymer-induced smaller surfactant aggregates driven by increase in entropy of the solution as a result of expulsion of the counterions from the ionic atmosphere around the surfactant aggregate. Because of the electrostatic interaction, hydrophobicity of the polymer-surfactant complex increases, leading to coacervation, and again solubilization in the hydrophobic core of the self-aggregated structure provided by the added excess CTAB. The tensiometric, conductometric, microcalorimetric, and turbidimetric techniques have been applied to address these problems.
与离子型表面活性剂和非离子型聚合物之间的相互作用相比，从物理化学角度来看，带有相反电荷的聚合物与表面活性剂之间的相互作用要复杂得多。在前者中，静电和疏水相互作用相互影响，而在后者中，疏水作用是主要因素。我们研究了水溶性聚阴离子羧甲基纤维素钠盐（NaCMC）与阳离子两亲物十六烷基三甲基溴化铵（CTAB）在水介质中的相互作用。在NaCMC-烷基三甲基溴化铵体系中，我们的研究结果与已报道的工作存在诸多差异，这被认为是取代度差异的影响，而取代度差异又反过来影响聚合物链的电荷密度。我们注意到，由静电力驱动的本体络合和界面相互作用同时存在。此后，由于反离子从表面活性剂聚集体周围的离子氛围中被排出，溶液熵增加，聚阴离子会对聚合物诱导形成的较小表面活性剂聚集体进行包裹。由于静电相互作用，聚合物-表面活性剂复合物的疏水性增加，导致凝聚，并且在添加的过量CTAB提供的自聚集结构的疏水核心中再次溶解。我们应用了张力测定、电导测定、微量量热测定和比浊测定技术来解决这些问题。
