Dynamic Simulation of Polymer Adsorption in Flowing Fluids for Design of Polymer Thin-film Materials

1132083库马尔，满意项目技术总结。由于其独特的电子特性，ab堆叠的双层和三层石墨烯在下一代光电和微处理器应用中显示出非凡的潜力。然而，这些有前途的材料需要新的合成方法，通过石墨剥落和先进的加工技术来有效地控制ab堆叠层的数量。解决方案石墨烯分散体是可印刷电子和纳米复合材料的有前途的原材料，最重要的是，这种方法代表了目前大规模生产AB堆叠双层和三层石墨烯的唯一可能途径。然而，自从2008年第一个石墨烯解决方案被报道以来，仍有许多未解决的问题和技术瓶颈阻碍了该领域的进展。尽管实验表明石墨烯层数的分布高度依赖于所使用的溶剂或表面活性剂的选择，但关于石墨烯与溶剂/表面活性剂分子之间相互作用的分子起源，包括这些相互作用与石墨烯溶液的胶体稳定性的关系，我们所知甚少。此外，无论采用何种方法制备溶液相石墨烯，其尺寸、形状和堆叠层数都是多分散的。必须开发能够直接控制脱落石墨烯薄片的尺寸和堆叠几何形状（通过缩小其分布）的工程方法。智力优势：该项目旨在通过大规模分子动力学模拟，了解悬浮石墨烯与周围溶剂/表面活性剂分子之间相互作用的起源。这些相互作用将通过计算溶剂或表面活性剂水溶液中石墨烯片之间的平均力势来量化，以建立分散石墨烯片的热力学性质库。结合分子动力学模拟和胶体聚集动力学理论的理论框架将被开发出来，以进一步设计最佳的溶剂/表面活性剂分子，以有效地稳定石墨烯分散体。实验上，层控石墨烯分散体将使用离子石墨嵌入化合物（gic）生产。通过仔细控制插层动力学，将合成高质量的Stage-2和Stage-3 GICs，它们有望成为两层和三层石墨烯分散体的优秀前驱体。将对石墨烯分散体进行系统表征，以优化剥离过程，使所产生的分散体足够浓缩，并且石墨烯片足够大，用于常规光刻，其中它们将沉积在目标衬底上。先进的分离技术也将被开发，以生产单分散的双层和三层石墨烯溶液。从提出的建模和实验中获得的新颖的基础和实践见解将用于指导电子器件的制造。这两家pi在胶体科学、工程纳米技术、计算机模拟和分子建模方面的专业知识的结合，将使设备制造的工程石墨烯解决方案取得快速进展。更广泛的影响和影响：一种新的先进技术的发展，在液相中剥离石墨烯，将大大提高生产ab堆叠双层和三层石墨烯的实际应用能力，如制造电子设备。此外，对石墨烯与其他分子之间相互作用的新的基本见解将有助于对石墨烯在液相中的动力学行为的整体理论和实践理解。最终，这些知识可以导致合理设计更好的石墨烯分散介质。所取得的建模和实验进展将被纳入课程（Blankschtein教授讲授的MIT课程10.55 -胶体和表面活性剂科学和Strano教授讲授的10.585 -工程纳米技术）和麻省理工学院的研讨会，这将使更多的科学听众了解石墨烯在液相中的分散和稳定的基本原理，以及在分子水平上对这些现象进行建模。值得注意的是，用于生产石墨烯分散体的原材料是石墨，石墨很容易大量获得。基于石墨的新材料/设备代表了现有技术的一种可行且经济的替代方案。本文提出的高导电性二维分散体的生产将潜在地用于导电油墨、可印刷电子产品和生物传感器的生产。技术对社会的影响从可卷曲显示器的发展到为糖尿病患者创造新型葡萄糖检测器。参与本研究的研究生和本科生将从本文提出的综合实验/建模研究中获得智力和专业知识。参与的pi和学生将参加麻省理工学院的周六工程丰富和发现（SEED）学院，以及少数民族工程与科学入门（MITES）项目，这两个项目都针对高中年龄的学生，并影响少数民族的招生。

1132083Kumar, SatishProject Technical Summary. Due to their distinct electronic properties, AB-stacked bilayer and trilayer graphene have shown extraordinary potential for next-generation optoelectronic and microprocessor applications. These promising materials, nevertheless, require new synthesis methods to effectively control the number of AB-stacked layers through graphite exfoliation and advanced processing techniques. Solution graphene dispersions are promising raw materials for printable electronics and nanocomposites, and most importantly, this approach represents the only possible route at this time for the mass-production of AB stacked bi- and tri-layer graphene. However, since the first graphene solution was reported in 2008, there are still many unanswered questions and technical bottlenecks that hinder the progress of this field. Although experiments have shown that the distribution of graphene layer numbers highly depends on the choice of solvents or surfactants used, very little is known about the molecular origin of the interactions between graphene and solvent/surfactant molecules, including correlating these interactions with the colloidal stability of the graphene solution. In addition, regardless of the methods used to produce solution-phase graphene, its size, shape, and number of stacked layers are all poly-disperse. Engineering approaches that can directly control the size and the stacking geometry (by narrowing their distributions) of the exfoliated graphene flakes have to be developed.Intellectual Merit:This project seeks to understand the origin of the interactions between suspended graphene with surrounding solvent/surfactant molecules via large-scale molecular dynamics simulations. These interactions will be quantified by calculating the potential of mean force between graphene sheets in solvents or aqueous surfactant solutions to establish a library of thermodynamic properties for dispersed graphene sheets. A theoretical framework that combines molecular dynamics simulations and kinetic theories of colloid aggregation will be developed to further design optimal solvent/surfactant molecules that can stabilize graphene dispersions efficiently. Experimentally, layer-controlled graphene dispersions will be produced using ionic graphite intercalation compounds (GICs). By carefully controlling the intercalation kinetics, high-quality Stage-2 and Stage-3 GICs will be synthesized, which are expected to be excellent precursors for bilayer and trilayer graphene dispersions. Systematic characterizations of graphene dispersions will be carried out to optimize the exfoliation process such that the produced dispersions are sufficiently concentrated, and that the graphene flakes are large enough, for conventional photolithography in which they will be deposited on a target substrate. Advanced separation techniques will also be developed to produce monodisperse bilayer and trilayer graphene solutions. The novel fundamental and practical insights gained from the proposed modeling and experiments will be used to guide the fabrication of electronic devices. The combined expertise of the two PIs across colloid science, engineering nanotechnology, computer simulations, and molecular modeling will enable rapid progress towards engineering graphene solutions for device manufacturing. Broader Impact and Outreach:The development of a novel advanced technique to exfoliate graphene in liquid phases will greatly increase the capability to produce AB-stacked bilayer and trilayer graphene for practical applications, such as fabricating electronic devices. In addition, novel fundamental insights into the interactions between graphene and other molecules will contribute to the overall theoretical and practical understanding of the kinetic behavior of graphene in the liquid phase. Ultimately, such knowledge can lead to the rational design of better media for graphene dispersions.The modeling and experimental advances made will be incorporated into courses (MIT course 10.55 - Colloid and Surfactant Science by Professor Blankschtein and 10.585 - Engineering Nanotechnology by Professor Strano) and workshops at MIT that will expose a larger scientific audience to the fundamentals of graphene dispersion and stabilization in liquid phases, as well as to modeling these phenomena at the molecular level. It is noteworthy that the raw material used to produce the graphene dispersions is graphite, which is readily available in large quantities. New materials/devices based on graphite represent a viable and economical alternative to existing technologies. The production of the highly-conductive, two-dimensional dispersions proposed here will be potentially useful for the production of conducting inks, printable electronics, and biological sensors. The technological impact to society extends from the development of rollable displays to the creation of novel glucose detectors for diabetics. The students involved in the proposed research at both the graduate an undergraduate level will gain intellectually and professionally from the integrated experimental/modeling research proposed here. The PIs and students involved will participate in the Saturday Engineering Enrichment and Discovery (SEED) Academy at MIT, as well as in the Minority Introduction to Engineering and Science (MITES) program, both of which target high school age students and influence minority recruitment.