Rheology of monodisperse latices
Rheology of monodisperse latices
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DOI：
10.1016/0001-8686(72)80001-0
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发表时间：
1972
影响因子：
15.6
通讯作者：
I. Krieger
中科院分区：
文献类型：
--
作者：
I. Krieger
单分散胶乳的流变学113非牛顿粘度和含时触变性等流变学异常。这种流变学上有趣的流体的共同结构特征是存在流动单元，要么是胶体颗粒，要么是大分子，它们的尺寸比悬浮介质的分子大，但仍然小到足以表现出显著的旋转和平移布朗运动。(在大分子的情况下，内部布朗运动也可能起到重要作用。)因此，流体的结构类似于大分子气体，空隙空间被牛顿连续体取代。对这种系统中的平衡和输运性质进行理论处理的适当框架将是统计流体力学，这是一个尚未开发的领域。在气体的统计力学处理中，它的有用抽象是硬球模型。在考虑和不考虑附加吸引势的情况下，该模型对Re~11气体的平衡和输运性质产生了许多有价值的见解。硬球在胶体理论中也占有重要的地位，爱因斯坦在研究稀悬浮液的粘度时采用了硬球，Verwey和Overbeek在胶体稳定性的经典研究中采用了硬球，柯克伍德和Mazur3用来表示球状蛋白质中的聚集。单分散胶乳的制备和表征的最新进展有望极大地提高这种方法的实用性，这使得实验学者能够接近理论家理想的具有显著保真度的硬球状胶体。“Laex”一词最初是指某些植物的乳状汁液，如印度橡胶树(Ifcvea Brsiierzsis)，HNS已扩展到通过乳液聚合产生的合成聚合物的水分散液。合成乳胶中的聚合物颗粒是近乎完美的球体，在流变学研究中遇到的应力下，它们的变形可以忽略不计。虽然典型胶乳中的颗粒直径分布不均匀(异质分散)，但通过特殊的乳液聚合技术可以生产高度单分散的胶乳(图1)。这些新产品，加上它们的提纯、颗粒电荷控制和在非水介质中重新分散的技术，使理论和实验之间的新一轮对抗成为可能。
RHEOLOGY OF MONODISPERSE LATICES 113 such rheological anomalies as non-Newtonian viscosity and time-dependent thixotropy. The common structural feature unifying this rheologically interesting cla’ss of fluids is the presence of flow units, either colloidal particles or macromolecules, whose dimensions are large compared with molecules of the suspending medium, while still small enough to exhibit significant rotatory and translatory Brownian movement.(In the case of macromolecules, internal Brownian movement may also play a significant role.) The structure of the fluid thus resembles a gas of large molecules, with the void space replaced by a Newtonian continuum. The proper framework for theoretical treatment of equilibrium and transport properties in such a system would be statistical hydrodynamics, an as yet underdeveloped field. In the statistical-mechanical treatment of gases, it useful abstraction is the hard-sphere model. Treated both with and without an added attractive potential, this model has yielded much valuable insight into equilibrium and transport properties of re~ 11 gases. The hard sphere has also found an important place in the theory of colloids, having been adopted by Einstein t in his study of the viscosity of dilute suspensions, by Verwey and Overbeek’in their classical investigation of colloid stability, and by Kirkwood and Mazur3 to represent clustering in globular proteins. The usefulness of this approach promises to be greatly enhanced by recent developments in the Droduction and characterization of monodisperse latices, which permit th: cxperimentalist to approach the theoretician’s ideal of a hard-sphere colloid with remarkable fidelity.The word “latex”, originally coined to denote the milky sap from certain plants such as the India-rubber tree (Ifcvea brusiiierzsis), hns been extended to aqueous dispersions of synthetic polymers as produced by emulsion polymerization. The polymer particles in synthetic laticcs are near-perfect spheres, which deform negligibly under the stresses encountered in rheological studies. While the distribution of particle diameters in a typical latex is non-uniform (heterodisperse), highly monodisperse latices (Fig. 1) can be produced by special techniques of emulsion polymerization4. These new products, together with techniques for their purification, control of particle charge, and redispersal in non-aqueous media, make possible a renewed confrontation between theory and experiment.