Local Confinement Controls Diffusive Nanoparticle Dynamics in Semidilute Polyelectrolyte Solutions
Local Confinement Controls Diffusive Nanoparticle Dynamics in Semidilute Polyelectrolyte Solutions
复制标题
局部限制控制半稀聚电解质溶液中的扩散纳米粒子动力学
DOI：
10.1021/acs.langmuir.0c01402
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发表时间：
2020
期刊：
影响因子：
3.9
通讯作者：
Conrad, Jacinta C.
中科院分区：
文献类型：
--
作者：
Slim, Ali H.;Poling-Skutvik, Ryan;Conrad, Jacinta C.
我们用荧光显微镜研究了直径从100到790 nm的聚苯乙烯颗粒在稀相和半稀相聚苯磺酸钠(NaPSS)溶液中的迁移率。我们通过改变溶液的离子强度来调节聚合物的构象。纳米颗粒的均方位移在所有的时间尺度上都随时间线性演化，表明了Fickian扩散动力学。根据斯托克斯-爱因斯坦图解，在高离子强度的溶液中，链采用随机游动构象，粒子动力学与体相的零剪切速率粘度相耦合。然而，在低离子强度的溶液中，随着聚合物浓度的增加，颗粒动力学非单调地偏离总体预测，并且不能被现有的模型准确地预测。这些非单调动力学与粒子位移分布的非高斯性直接相关，表明随着聚电解质浓度的增加，出现了局部约束长度尺度。
We investigate the mobility of polystyrene particles ranging from 100 to 790 nm in diameter in dilute and semidilute sodium polystyrene sulfonate (NaPSS) solutions using fluorescence microscopy. We tune the polymer conformations by varying the ionic strength of the solution. The nanoparticle mean-squared displacements evolve linearly with time at all time scales, indicating Fickian diffusive dynamics. In solutions of high ionic strength, chains adopt a random walk conformation and particle dynamics couple to the bulk zero-shear rate viscosity, according to the Stokes–Einstein picture. In solutions of low ionic strength, however, particle dynamics nonmonotonically deviate from bulk predictions as polymer concentration increases and are not accurately predicted by the available models. These nonmonotonic dynamics directly correlate with the non-Gaussianity in distributions of particle displacements, suggesting the emergence of a local confining length scale as polyelectrolyte concentration increases.