Inorganic & Physical Chemistry Laboratory, CSIR - Central Leather Research Institute, Adyar, Chennai-600020, India.
NMR, CATERS, CSIR - Central Leather Research Institute, Adyar, Chennai-600020, India.
Phys Chem Chem Phys. 2021 Jun 16;23(23):13170-13180. doi: 10.1039/d0cp06227h.
The interaction of copolymer L61 i.e., (EO)2(PO)32(EO)2 (where EO and PO are ethylene and propylene oxides, respectively) with surfactant SDS (sodium dodecylsulfate) in relation to their self-aggregation, dynamics and microstructures has been physicochemically studied in detail employing the Nuclear Magnetic Resonance (NMR), Electron Paramagnetic Resonance (EPR), Small-Angle Neutron Scattering (SANS), and Freeze-Fracture Transmission Electron Microscopy (FF-TEM) methods. The NMR self-diffusion study indicated a synergistic interaction between SDS and L61 forming L61-SDS mixed complex aggregates, and deuterium (2H) NMR pointed out the nonspherical nature of these aggregates with increasing [L61]. EPR spectral analysis of the motional parameters of 5-doxyl steraric acid (5-DSA) as a spin probe provided information on the microviscosity of the local environment of the L61-SDS complex aggregates. SANS probed the geometrical aspects of the SDS-L61 assemblies as a function of both [L61] and [SDS]. Progressive evolution of the mixed-aggregate geometries from globular to prolate ellipsoids with axial ratios ranging from 2 to 10 with increasing [L61] was found. Such morphological changes were further corroborated with the results of 2H NMR and FF-TEM measurements. The strategy of the measurements, and data analysis for a concerted conclusion have been presented.
聚氧乙烯-聚氧丙烯共聚物 L61（EO）2（PO）32（EO）2（其中 EO 和 PO 分别为乙烯氧化物和丙烯氧化物）与表面活性剂 SDS（十二烷基硫酸钠）的相互作用及其自组装、动力学和微观结构已通过核磁共振（NMR）、电子顺磁共振（EPR）、小角中子散射（SANS）和冷冻断裂透射电子显微镜（FF-TEM）等物理化学方法进行了详细研究。NMR 自扩散研究表明 SDS 和 L61 之间存在协同相互作用，形成 L61-SDS 混合复杂聚集体，氘（2H）NMR 指出这些聚集体具有非球形性质，且随着[L61]的增加而增加。作为旋转探针的 5-二氧杂戊环硬脂酸（5-DSA）的 EPR 光谱分析提供了关于 L61-SDS 配合物聚集体局部环境微粘度的信息。SANS 探测了 SDS-L61 组装物的几何形状，作为[L61]和[SDS]的函数。发现随着[L61]的增加，混合聚集体的几何形状从球形逐渐演变为长椭球形，纵横比范围从 2 到 10。这种形态变化进一步得到了 2H NMR 和 FF-TEM 测量结果的证实。本文提出了协同结论的测量策略和数据分析。
