Integrated multi-scale, multi-tool, modeling of transport in polymer-colloid assemblies

PI: Larson， ronald提案号：1602183提议研究的目标是开发涂层材料性能的预测方法，甚至通过从分子水平上设计材料来规定这些性能。这项研究的结果将在工程和工业中找到许多应用，因为涂层材料在日常生活中的效用是明确的。我们周围的大多数物体都涂上了一层材料，这种材料要么增强了它们的实用性，要么延长了它们的寿命（电脑和平板电脑屏幕、家具、金属物体和工具、墙壁等）。虽然在多尺度建模领域已经有了很大的兴趣和努力，但基于多尺度建模的胶体尺度输运性质的成功预测很少，如果有的话，从具有大规模商业利益的材料的原子输入开始。在这里，我们建议整合近年来发展的一套方法来预测表面活性剂、聚合物和胶体组成对乳胶漆流变性能的影响。乳胶漆含有表面活性剂分子，具有疏水性“贴纸”端基的聚合物分子，以及由聚合物分子桥接形成瞬态网络的胶体颗粒。要实现和集成的模拟工具是原子、粗粒（CG）和隐式溶剂CG水平的分子动力学模拟，使用有限可扩展（FENE）弹簧模型使用粗粒聚合物链的布朗动力学模拟，用于跟踪胶体颗粒对之间桥接聚合物链数量的种群平衡方法，以及用于计算剪切流动中胶体颗粒流体动力相互作用的Stokesian动力学方法。还将开发计算微观转变的自由能的方法，例如桥接到环状链的转变的自由能，以及结合到胶体颗粒的聚合物链的压缩的自由能。虽然在过去的十年里，Larson团队已经开发或利用了所有这些工具，并且已经在热力学层面上进行了许多方法的集成，但提出的新研究是将这些方法的输运特性映射到彼此之间，以便在最精细的水平上确定输运率，从而允许指定粗粒度方法的输入参数和时间尺度。通过与实验数据的比较，还将验证和改进该映射。该项目的完成将导致一套互锁的建模工具，不仅可以预测乳胶漆的流变性能，而且将为许多其他复杂材料和多尺度运输过程的建模建立一个范例。更广泛的影响包括与工业的互动。我们将向少数族裔学生伸出援手，并通过在密歇根大学的工作和陶氏化学公司的暑期实习，招募和培训一名博士生。将开发一个用于预测聚合物/胶体材料流变特性的开源软件包，并与英国爱丁堡大学和达勒姆大学建立国际合作关系。

PI: Larson, RonaldProposal Number: 1602183The goal of the proposed research is to develop predictive methods for coating material properties and to even prescribe these properties by designing materials from the molecular level up. The results of this research would find many applications in engineering and in the industry, since the utility of coating materials in everyday life is unequivocal. Most of the objects around us are coated with a material that either enhances their usefulness or their life time (computer and tablet screens, furniture, metallic objects and tools, walls etc.). While there has been great interest and effort in the area of multi-scale modeling, there have been few, if any, successful predictions of colloidal scale transport properties based on multi-scale modeling starting with atomistic inputs for materials of large-scale commercial interest. Here, it is proposed to integrate a set of methods developed in recent years to allow prediction of the impact of surfactant, polymer, and colloidal composition on the rheological properties of latex coatings. Latex coatings contain surfactant molecules, polymer molecules with hydrophobic "sticker" end groups, and colloidal particles that are bridged by the polymer molecules to form a transient network. The simulation tools to be implemented and integrated are molecular dynamics simulations at the atomistic, coarse-grained (CG) and implicit-solvent CG levels, Brownian dynamics simulations using coarse-grained polymer chains using finitely extensible (FENE) spring models, population balance methods for tracking numbers of bridging polymer chains between pairs of colloidal particles, and Stokesian dynamics methods for computing the hydrodynamic interactions of colloidal particles undergoing shear flow. Also to be exploited are methods of computing free energies of microscopic transitions, such as free energy of transition of a bridging to a looping chain, and free energy of compression of polymer chains bound to colloidal particles. While all of these tools have been developed or exploited in the Larson group over the past decade, and integration of many of the methods has been carried out at the level of thermodynamics, the proposed new research is to map the transport properties of these methods onto each other, so that transport rates determined at the finest levels allow input parameters and time-scales of coarser-grained methods to be specified. The mapping will also be validated and improved upon, through comparison with experimental data. Accomplishment of this project will lead to a set of inter-locking modeling tools that will not only allow prediction of the rheological properties of latex coatings, but will establish a paradigm to be followed for modeling many other complex materials and multi-scale transport processes. Broader impacts include interactions with industry. An outreach to minority students will be undertaken and a Ph.D. student will be recruited and trained both through the work at Michigan and through summer internships at Dow Chemical Company. An open source software package for prediction of the rheological properties of polymer/colloid materials will be developed and international collaborations with Edinburgh University and Durham University at the UK will be established.