Qin Jian, Priftis Dimitrios, Farina Robert, Perry Sarah L, Leon Lorraine, Whitmer Jonathan, Hoffmann Kyle, Tirrell Matthew, de Pablo Juan J
Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States.
Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States.
ACS Macro Lett. 2014 Jun 17;3(6):565-568. doi: 10.1021/mz500190w. Epub 2014 May 30.
We consider polyelectrolyte solutions which, under suitable conditions, phase separate into a liquid-like coacervate phase and a coexisting supernatant phase that exhibit an extremely low interfacial tension. Such interfacial tension provides the basis for most coacervate-based applications, but little is known about it, including its dependence on molecular weight, charge density, and salt concentration. By combining a Debye-Hückel treatment for electrostatic interactions with the Cahn-Hilliard theory, we derive explicit expressions for this interfacial tension. In the absence of added salts, we find that the interfacial tension scales as (η/η-1) near the critical point of the demixing transition, and that it scales as η far away from it, where is the chain length and η measures the electrostatic interaction strength as a function of temperature, dielectric constant, and charge density of the polyelectrolytes. For the case with added salts, we find that the interfacial tension scales with the salt concentration ψ as (1-ψ/ψ) near the critical salt concentration ψ. Our predictions are shown to be in quantitative agreement with experiments and provide a means to design new materials based on polyelectrolyte complexation.
我们考虑聚电解质溶液，在合适条件下，它会相分离成类似液体的凝聚相和共存的上清相，这两相之间的界面张力极低。这种界面张力是大多数基于凝聚相的应用的基础，但人们对其了解甚少，包括它对分子量、电荷密度和盐浓度的依赖性。通过将用于静电相互作用的德拜 - 休克尔处理与相场Cahn - Hilliard理论相结合，我们推导出了这种界面张力的显式表达式。在不添加盐的情况下，我们发现在相分离转变的临界点附近，界面张力与(η/η - 1)成比例，而在远离临界点处，它与η成比例，其中是链长，η作为温度、介电常数和聚电解质电荷密度的函数衡量静电相互作用强度。对于添加盐的情况，我们发现在临界盐浓度ψ附近，界面张力与盐浓度ψ的关系为(1 - ψ/ψ)。我们的预测结果与实验结果在定量上吻合，为基于聚电解质络合设计新材料提供了一种方法。
