UNS: Predicting the Interfacial Activity of Complex Grafted Nanoparticles

#1510635 Riggleman，Robert A.许多消费品，从化妆品、洗涤剂和用于石油回收的液体，都需要稳定两种不相容的液体(例如，油和水)作为乳状液，其中一相(通常是油)作为稳定的液滴分散在第二相(水)中。最近，实验表明，加入表面接枝了聚合链的纳米粒子是稳定这些乳液的一种异常有效和廉价的方法，但稳定的机理仍然知之甚少。该方案的研究目标是研究接枝高分子链的化学结构对接枝纳米粒子界面性质的影响。我们将研究聚合物刷在孤立纳米粒子上的构象，多个纳米粒子之间的相互作用，包括它们对界面张力和界面自组装的影响，以及带电对接枝高聚物链的影响。这些计算是由我们小组开发的最新模拟技术实现的。我们的教育目标包括培养聚合物科学和工程方面的研究生，以及最先进的模拟技术。我们将继续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粒子的热力学越来越感兴趣，这些纳米粒子用于分离膜和采油液等应用。通过仔细调节颗粒核心、接枝链和组成接枝颗粒基质的任何组分之间的相互作用，只需控制聚合物的聚集和分散状态，就可以轻松地控制光学和机械性能。最近的实验表明，接枝的纳米颗粒在油和水的乳状液中表现出显著的界面活性，并且它们在低得令人惊讶的浓度下能够在很长一段时间内稳定乳状液。此外，接枝结构的影响根本没有被探索；合成化学的最新进展使接枝两嵌段聚合物、均聚物混合物或片状(Janus)接枝到纳米颗粒表面成为可能。实验者可以使用的大参数空间产生了对分子建模的需求，分子建模可以引导实验走向显示出最有希望应用于各种应用的系统。这项提议的目的是使用我的团队最近开发的场论模拟框架来检查复杂的接枝纳米粒子的结构和界面性质。我们将考察纳米粒子表面的混合刷子、双嵌段聚合物刷子和Janus刷子作为粒子核心大小、接枝密度、刷子组成以及与基质相相互作用的函数。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，同时结合离子溶剂化和形成界面的两相之间的介电失配的影响。总体而言，我们预计我们的结果将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，为石油开采流体和各种消费产品的设计提供基本见解。除了接受过聚合物物理和最先进的分子建模技术培训的博士生之外，我们的工作还包括大量的教育和推广部分，包括本科生(可能是高中生)的研究、课程开发以及对整个科学界的推广。我们的实验室目前有一名本科生与我们合作，他与人共同撰写了一篇论文。2014年夏天，我们邀请了一名当地的高中生来我们的实验室，进行聚合物熔体的分子动力学模拟。我们正在为专门的分子建模课程以及引入和发展场论模拟框架的广泛的一年级统计力学课程开发课程模块。最后，除了推动我们工作的标准会议外，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。我们希望扩大场论模拟框架的应用和使用，我们相信，通过降低进入门槛可以最有效地实现这一点。让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.