Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA.
J Chem Phys. 2011 May 7;134(17):174903. doi: 10.1063/1.3578183.
Tracer particle microrheology using diffusing wave spectroscopy-based microrheology is demonstrated to be a useful method to study the dynamics of aqueous Pluronic™ F108 solutions, which are viewed as solutions of repulsive soft spheres. The measured zero-shear microviscosity of noncrystallizing micellar dispersions indicates micelle corona dehydration upon increasing temperature. Colloidal sphere thermal motion is shown to be exquisitely sensitive to the onset of crystallization in these micellar dispersions. High temperature dynamics are dominated by an apparent soft repulsive micelle-micelle interaction potential indicating the important role played by lubrication forces and ultimately micelle corona interpenetration and compression at sufficiently high concentrations. The measured microscopic viscoelastic storage and loss moduli are qualitatively similar to those experimentally observed in mechanical measurements on colloidal dispersions and crystals, and calculated from mode coupling theory of colloidal suspensions. The observation of subdiffusive colloidal sphere thermal motion at short time-scales is strong evidence that the observed microscopic viscoelastic properties reflect the dynamics of individual micelles rather than a dispersion of micellar crystallites.
基于扩散波光谱的示踪粒子微流变学被证明是一种研究水相 Pluronic™ F108 溶液动力学的有用方法，因为这些溶液被视为斥力软球的溶液。在升温过程中，非结晶胶束分散体的测量零切微粘度表明胶束冠层脱水。胶体球热运动对这些胶束分散体中结晶的开始表现出极高的敏感性。高温动力学主要由一个明显的软斥力胶束-胶束相互作用势主导，这表明润滑作用以及最终胶束冠层相互渗透和压缩在足够高的浓度下发挥了重要作用。测量的微观粘弹储能和损耗模量与胶体分散体和晶体的机械测量实验中观察到的那些定性相似，并从胶体悬浮液的模式耦合理论计算得出。在短时间尺度上观察到亚扩散胶体球热运动，这有力地证明了所观察到的微观粘弹性性质反映了单个胶束的动力学，而不是胶束微晶的分散体。
