Department of Materials Science and Engineering, University of California- Los Angeles, Los Angeles, CA, 90095, USA.
Department of Chemistry and Biochemistry, University of California- Los Angeles, Los Angeles, CA, 90095, USA.
Sci Rep. 2023 Jan 31;13(1):1791. doi: 10.1038/s41598-023-28308-6.
Introducing short-range attractions in Brownian systems of monodisperse colloidal spheres can substantially impact their structures and consequently their optical transport and rheological properties. Here, for size-fractionated colloidal emulsions, we show that imposing an intermediate strength of attraction, well above but not much larger than thermal energy ([Formula: see text] [Formula: see text], through micellar depletion leads to a striking notch in the measured inverse mean free path of optical transport, [Formula: see text], as a function of droplet volume fraction, [Formula: see text]. This notch, which appears between the hard-sphere glass transition, [Formula: see text], and maximal random jamming, [Formula: see text], implies the existence of a greater population of compact dense clusters of droplets, as compared to tenuous networks of droplets in strongly attractive emulsion gels. We extend a prior decorated core-shell network model for strongly attractive colloidal systems to include dense non-percolating clusters that do not contribute to shear rigidity. By constraining this extended model using the measured [Formula: see text], we improve and expand the microrheological interpretation of diffusing wave spectroscopy (DWS) experiments made on attractive colloidal systems. Our measurements and modeling demonstrate richness and complexity in optical transport and shear rheological properties of dense, disordered colloidal systems having short-range intermediate attractions between moderately attractive glasses and strongly attractive gels.
在单分散胶体球的布朗体系中引入短程吸引力会显著影响它们的结构，从而影响它们的光学传输和流变性能。在这里，对于分级胶体乳液，我们通过胶束耗尽表明，施加中等强度的吸引力（远高于但不大大高于热能 ([Formula: see text] [Formula: see text]）会导致测量的光学传输逆平均自由程 [Formula: see text] 作为液滴体积分数 [Formula: see text] 的函数的显著缺口。这个缺口出现在硬球玻璃化转变 [Formula: see text] 和最大随机堵塞 [Formula: see text] 之间，意味着存在更多的紧密密集液滴簇，而不是在强烈吸引力乳液凝胶中稀疏的液滴网络。我们将用于强吸引力胶体系统的先前的修饰核壳网络模型扩展到包括不贡献剪切刚度的密集不可渗透簇。通过使用测量的 [Formula: see text] 来约束这个扩展模型，我们改进并扩展了在有吸引力的胶体系统上进行的扩散波光谱 (DWS) 实验的微流变解释。我们的测量和建模证明了具有中等吸引力玻璃和强吸引力凝胶之间的短程中间吸引力的密集、无序胶体系统在光学传输和剪切流变性能方面具有丰富性和复杂性。
