Rheological modifiers are added to formulations to tune rheology, enable function and drive phase changes requiring an understanding of material structure and properties. We characterize two colloidal rod systems during phase transitions using multiple particle tracking microrheology, which measures the Brownian motion of probes embedded in a sample. These systems include a colloid (monodisperse polyamide or polydisperse hydrogenated castor oil), surfactant (linear alkylbenzene sulfonate [LAS]), and nonabsorbing polymer (polyethylene oxide [PEO]) which drives gelation by depletion interactions. Phase transitions are characterized at all concentrations using time-cure superposition. We determine that rheological evolution depends on LAS:colloid. The critical PEO concentration required to form a gel, c_c/c*, is independent of LAS:colloid, critical relaxation exponent, n, is dependent on LAS:colloid, and both are independent of colloid polydispersity. n indicates the material structure at the phase transition. At LAS:colloid > 16, the scaffold is a tightly associated network and at LAS:colloid = 16 a loosely associated network.

中文翻译：

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多分散和单分散胶体棒体系中相变的流变特性

流变改性剂被添加到配方中以调整流变性，实现功能并推动需要了解材料结构和特性的相变。我们使用多粒子跟踪微流变学表征相变期间的两个胶体棒系统，该微流变学测量嵌入样品中的探针的布朗运动。这些系统包括胶体（单分散聚酰胺或多分散氢化蓖麻油）、表面活性剂（线性烷基苯磺酸盐 [LAS]）和非吸收性聚合物（聚环氧乙烷 [PEO]），它们通过耗尽相互作用驱动凝胶化。使用时间固化叠加在所有浓度下表征相变。我们确定流变演化取决于LAS:colloid。形成凝胶所需的临界 PEO 浓度，c _c / c * 与LAS:colloid无关，临界松弛指数n取决于LAS:colloid，并且两者都与胶体多分散性无关。n表示相变时的材料结构。在LAS:colloid  > 16 处，支架是一个紧密关联的网络，在LAS:colloid  = 16 处是一个松散关联的网络。