Kwon Taejin, Wilcoxson Tanner A, Milliron Delia J, Truskett Thomas M
McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, USA.
J Chem Phys. 2022 Nov 14;157(18):184902. doi: 10.1063/5.0125125.
Colloids that attractively bond to only a few neighbors (e.g., patchy particles) can form equilibrium gels with distinctive dynamic properties that are stable in time. Here, we use a coarse-grained model to explore the dynamics of linked networks of patchy colloids whose average valence is macroscopically, rather than microscopically, constrained. Simulation results for the model show dynamic hallmarks of equilibrium gel formation and establish that the colloid-colloid bond persistence time controls the characteristic slow relaxation of the self-intermediate scattering function. The model features re-entrant network formation without phase separation as a function of linker concentration, centered at the stoichiometric ratio of linker ends to nanoparticle surface bonding sites. Departures from stoichiometry result in linker-starved or linker-saturated networks with reduced connectivity and shorter characteristic relaxation times with lower activation energies. Underlying the re-entrant trends, dynamic properties vary monotonically with the number of effective network bonds per colloid, a quantity that can be predicted using Wertheim's thermodynamic perturbation theory. These behaviors suggest macroscopic in situ strategies for tuning the dynamic response of colloidal networks.
仅与少数相邻粒子产生吸引性键合的胶体（例如，斑图粒子）可以形成具有独特动态特性且随时间稳定的平衡凝胶。在此，我们使用一个粗粒化模型来探究斑图胶体连接网络的动力学，该网络的平均化合价在宏观而非微观层面受到约束。该模型的模拟结果显示了平衡凝胶形成的动态特征，并确定了胶体 - 胶体键的持续时间控制着自中间散射函数的特征慢弛豫。该模型的特点是随着连接体浓度的变化，会形成无相分离的折返网络，其中心位于连接体末端与纳米颗粒表面结合位点的化学计量比。偏离化学计量比会导致连接体匮乏或连接体饱和的网络，其连通性降低，特征弛豫时间更短，活化能更低。在折返趋势的背后，动态特性随每个胶体有效网络键的数量单调变化，这个数量可以使用韦特海姆的热力学微扰理论来预测。这些行为为调整胶体网络的动态响应提供了宏观原位策略。
