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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Rotational Relaxation of Nondipolar Probes in Triton X-100 Micelles in the Presence of Added Salt: Correlation of Lateral Diffusion Coefficient with 'Dry' Micelle Radius
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Rotational Relaxation of Nondipolar Probes in Triton X-100 Micelles in the Presence of Added Salt: Correlation of Lateral Diffusion Coefficient with 'Dry' Micelle Radius

机译：存在盐的情况下，Triton X-100胶束中非偶极探针的旋转弛豫：横向扩散系数与“干”胶束半径的相关性

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摘要

In continuation of our efforts to understand the dynamics of solubilized species in large nonionic micelles, rotational relaxation of two structurally similar nondipolar probes, 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) and 1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP), has been studied in Triton X-100 (TX-100) micelles in the presence of added salt. According to very recent light scattering studies, the hydrodynamic radius of TX-100 micelles increased by a factor of 2.2 upon the addition of 2.0 M NaCl due to increase in both the aggregation number and mechanically entrapped water. The micelles also get dehydrated in the presence of electrolyte due to decrease in the thermodynamically bound water, and consequently the "dry" micelle radius also increases, but only by a factor of 1.5. Time-resolved anisotropy of both the probes, DMDPP and DPP, in TX-100 micelles decays as a sum of two exponentials with two time constants, one corresponding to a fast reorientation time and the other to a slow one, over the entire range of salt concentration. The results are analyzed in terms of a two-step model consisting of fast-restricted rotation of the probe and slow lateral diffusion of the probe in the micelle that are coupled to the rotation of the micelle as a whole. However, as the concentration of NaCl is increased from 0.0 to 2.0 M, there is only a marginal increase (37% for DMDPP and 19% for DPP) in the slow component and almost no change in the fast component for both the probes. The lateral diffusion coefficients of both the probes obtained from their respective slow components are correlated with the dry micelle radius.
机译：在继续努力了解大的非离子胶束中可溶物质的动力学过程中，两个结构相似的非偶极探针，即2,5-二甲基-1,4-二氧代-3,6-二苯基吡咯并[3,4-c]的旋转弛豫在添加盐的存在下，在Triton X-100（TX-100）胶束中研究了吡咯（DMDPP）和1,4-二氧代-3,6-二苯基吡咯并[3,4-c]吡咯（DPP）。根据最近的光散射研究，由于聚集数量和机械截留水的增加，在添加2.0 M NaCl后，TX-100胶束的流体力学半径增加了2.2倍。由于热力学结合的水的减少，胶束在电解质的存在下也会脱水，因此“干”胶束半径也增加了，但仅增加了1.5倍。在TX-100胶束中，两种探针DMDPP和DPP的时间分辨各向异性随着具有两个时间常数的两个指数之和的衰减而衰减，一个对应于快速重新定向时间，另一个对应于一个慢速定向，在整个范围内。盐浓度。根据两步模型分析结果，该模型由探针的快速限制旋转和探针在胶束中的缓慢侧向扩散组成，这与整个胶束的旋转有关。但是，随着NaCl浓度从0.0 M增加到2.0 M，慢速组分仅略有增加（DMDPP为37％，DPP为19％），而两种探针的快速组分几乎没有变化。从它们各自的慢速组分获得的两种探针的横向扩散系数与干胶束半径相关。

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