UNS: Predicting the Interfacial Activity of Complex Grafted Nanoparticles

作者：Riggleman，Robert A.从化妆品、洗涤剂和用于采油的流体的许多消费品需要两种不混溶流体（例如，油和水）作为乳液，其中一相（通常为油）作为稳定的液滴分散在第二相（水）中。最近，实验表明，添加具有接枝到其表面的聚合物链的纳米尺寸的颗粒是用于稳定这些乳液的异常有效且廉价的方法，但是稳定的机制仍然知之甚少。本论文的研究目的是研究接枝聚合物链的化学性质对接枝纳米粒子界面性质的影响。我们将研究孤立的纳米粒子上的聚合物刷的构象，多个纳米粒子的相互作用，包括它们对界面张力和界面自组装的影响，我们将研究接枝聚合物链上的电荷的影响。这些计算是由我们小组最近开发的模拟技术实现的。我们的教育目标包括培养高分子科学和工程以及最先进的模拟技术的研究生。我们将继续我们小组的努力，让本科生和高中生参与我们的研究。最后，我们将通过开发和发布执行我们计算的模拟代码来影响更广泛的科学界。近年来，人们对聚合物功能化纳米颗粒的热力学越来越感兴趣，这些纳米颗粒可用于分离膜和石油萃取液等应用。通过仔细调节颗粒核、接枝链和构成接枝颗粒的主体基质的任何组分之间的相互作用，可以简单地通过控制聚合物的聚集和分散状态来容易地控制光学和机械性能。最近，实验表明，接枝纳米粒子在油和水乳液中表现出显著的界面活性，并且它们在令人惊讶的低浓度下在长时间内稳定乳液方面非常有效。此外，接枝结构的影响还没有被探索，在所有的合成化学的最新进展，使接枝二嵌段聚合物，均聚物的混合物，或补丁（Janus）接枝在纳米粒子的表面上。实验者可用的这个大的参数空间产生了对分子建模的需要，该分子建模可以引导实验朝向显示出最有希望用于各种应用的系统。这个提议的目的是使用我的小组最近开发的场论模拟框架来研究复杂接枝纳米颗粒的结构和界面性质。我们将研究混合刷，二嵌段聚合物刷，和Janus刷在纳米粒子的表面上作为一个功能的颗粒核心大小，接枝密度，刷组合物，和与基体相的相互作用。最后，我们将研究当其中一种聚合物携带电荷时，图像如何变化，同时将离子溶剂化和两相之间的介电失配的影响结合起来，从而形成界面。总的来说，我们希望我们的结果对未来实验的设计产生重大影响。我们的努力将对社会产生广泛的影响，为石油开采和各种消费品的流体设计提供基本见解。除了在聚合物物理学和最先进的分子建模技术培训的博士生，我们的工作有大量的教育和推广的组成部分，涉及本科生（和潜在的高中生）的研究，课程开发，并推广到一般的科学界。我们的实验室目前有一名本科生与我们合作，共同撰写了一篇论文，2014年夏天，我们有一名当地高中生访问我们的实验室，进行聚合物熔体的分子动力学模拟。我们正在为专业的分子建模课程以及广泛的第一年统计力学课程开发课程模块，这些课程介绍和开发场论模拟框架。最后，除了标准的会议推广我们的工作，我们正在开发一个代码库，我们可以发布和免费向公众发布。我们希望拓宽场论模拟框架的应用和使用，我们相信这可以通过降低进入门槛来最有效地实现。使我们的代码广泛可用是这一愿景的关键部分。

#1510635Riggleman, Robert A. Numerous consumer products ranging from cosmetics, detergents, and fluids for oil recovery require the stabilization of two immiscible fluids (e.g., oils and water) as an emulsion, where one phase (typically the oil) is dispersed as stable droplets in the second phase (water). Recently, experiments have shown that adding nanometer-sized particles that have polymer chains grafted to their surface is an unusually effective and inexpensive method for stabilizing these emulsions, but the mechanism for stabilization remains poorly understood. The research goal of this proposal is to study the effect of the chemistry of the grafted polymer chains on the interfacial properties of grafted nanoparticles. We will study the conformations of the polymer brush on isolated nanoparticles, the interactions of multiple nanoparticles, including their effect on the interfacial tension and self-assembly at the interface, and we will study the effect of having charges on the grafted polymer chains. These calculations are enabled by recent simulation techniques developed in our group. Our educational goals include the training of graduate students in polymer science and engineering, and state-of-the-art simulation techniques. We will continue our group's effort at involving undergraduate and high school students in our research. Finally, we will impact the broader scientific community by developing and publishing simulation codes that perform our calculations.In recent years, there has been a growing interest in the thermodynamics of nanoparticles functionalized with polymers for use in applications such as separations membranes and oil extraction fluids. By carefully tuning the interactions between the particle cores, the grafted chains, and any components that make up the host matrix of the grafted particles, one can easily control optical and mechanical properties simply by controlling the aggregation and dispersion state of the polymer. Very recently, experiments have shown that grafted nanoparticles exhibit a remarkable interfacial activity in oil and water emulsions, and they are highly effective at stabilizing the emulsions over long periods of time at surprisingly low concentrations. Furthermore, the effect of the grafting architecture has not been explored at all; recent advances in synthetic chemistry enables grafting diblock polymers, a mixture of homopolymers, or patchy (Janus) grafting on the surface of nanoparticles. This large parameter space available to experimentalists creates a need for molecular modeling that can guide experiments toward systems that show the most promise for various applications. The goal of this proposal is to use a field theoretic simulations framework recently developed by my group to examine the structure and interfacial properties of complex grafted nanoparticles. We will examine mixed brushes, diblock polymer brushes, and Janus brushes on the surface of nanoparticles as a function of the particle core size, grafting density, brush composition, and interactions with the matrix phases. Finally, we will examine how the picture changes when one of the polymers carries a charge, while incorporating the effects of ion solvation and dielectric mismatch between the two phases creating the interface. Overall, we expect our results to have a significant impact on the design of future experiments. Our efforts will have a broad impact to society by providing fundamental insights into the design of fluids for oil extraction and a wide variety of consumer products. In addition to the doctoral students trained in polymer physics and state-of-the-art molecular modeling techniques, our work has a substantial education and outreach component involving undergraduate (and potentially high school student) research, course development, and outreach to the scientific community in general. Our lab has one undergraduate student currently working with us who has co-authored a paper, and in the summer of 2014 we had a local high school student visit our lab, performing molecular dynamics simulations of polymer melts. We are developing course modules both for specialized molecular modeling courses as well as broad first-year statistical mechanics courses that introduce and develop the field theoretic simulations framework. Finally, in addition to the standard conference meetings promoting our work, we are developing a code base that we can publish and freely release to the public. Our hope is to broaden the application and use of the field theoretic simulations framework, and we believe this can be most effectively achieved by lowering the barrier to entry. Making our codes widely available is a key part of that vision.