CAREER: Molecular Rheology of Architecturally Complex Polymers

1254340施罗德聚合物支撑着从消费产品到电子产品的无数技术。尽管这一领域最近取得了进展，但对缠绕聚合物溶液的流动特性缺乏充分的了解。聚合物加工中的一个主要挑战来自支化聚合物异常复杂的流动动力学，其中分子拓扑最终决定宏观材料响应。传统上，整体流变学方法被用来研究聚合物流动，但这些方法平均了单个分子的运动。为了克服这些挑战，需要一种新的分子方法来探测动力学。这项拟议的研究旨在使用单分子方法提供支化聚合物流动动力学的分子水平视图。将研究聚合物的应力松弛和纠缠梳状聚合物的非线性流动特性，并将实验得到的单个聚合物的数据与理论模型进行比较。这样，通过在主链和侧链支链上使用双色荧光染料，可以在分子水平上直接观察主链和支链的松弛。这项拟议的研究依赖于PI实验室开发的三项创新技术：(1)定制合成具有类似合成链性质的线状和支化单链DNA(SsDNA)聚合物，(2)在骨架和分支等特定结构位置对支化单链DNA聚合物进行双色标记，以及(3)允许受控流体流动的自动化微流控流动系统，结合纳米级聚合物构象的单分子成像。更广泛的影响。这项研究将提供一个详细的分子水平的纠缠拓扑网络的观点，从而建立了支化聚合物的分子性质与宏观流动性质(例如粘度和应力)之间的直接联系。建议的定制合成和分子成像相结合的方法将允许对具有定制性能的聚合物材料进行指导设计，从而产生所需的加工响应。通过这种方式，拟议的工作将为支化聚合物的改进加工和制造提供至关重要的见解。这项拟议的工作还将分子流变学的尖端研究与研究生和本科生的教育培训相结合，这是通过指导学生在协作工作空间中工作来完成的。教育外展将通过与伊利诺伊州iRise计划合作进行，该计划积极聘请Urbana-Champaign地区当地的K-12高中科学教师为课堂开发实验实验室，并指导代表人数较少的群体的初中生和高中生，特别注重通过动手实验激发人们对科学的兴趣。这项拟议的研究还包括参与伊利诺伊大学研究生教育多元文化工程招生(MERGE)计划，该计划旨在从工程学中代表性不足的群体中招收学生。

1254340SchroederPolymers underlie an untold number of technologies ranging from consumer products to electronics. Despite recent progress in the field, a full understanding of the flow properties of entangled polymer solutions is lacking. A major challenge in polymer processing arises from the unusually complex flow dynamics of branched polymers, wherein molecular topology ultimately determines macroscopic material response. Traditionally, bulk rheological methods have been used to study polymer flows, but these methods average away individual molecular motions. To overcome these challenges, a new molecular approach to probe dynamics is required.Intellectual Merit. The proposed research aims to provide a molecular-level view of branched polymer dynamics in flow using single molecule methods. Polymer stress relaxation and the non-linear flow properties of entangled comb polymers will be studied, and single polymer data obtained from experiments will be compared to theoretical models. In this way, direct observation of backbone and branch relaxation at the molecular level will be pursued, facilitated by using dual-color fluorescent dyes on the backbone and side-chain branches. The proposed research relies on three innovative technologies developed in the PI's lab: (1) custom synthesis of linear and branched single stranded DNA (ssDNA) polymers with properties similar to synthetic chains, (2) dual-color labeling of branched ssDNA polymers at architecturally-specific locations such as backbones and branches, and (3) automated microfluidic-based flow systems that allow for controlled fluid flows, combined with single molecule imaging of polymer conformations with nanoscale resolution. Broader Impacts. This research will provide a detailed molecular-level view of entangled topological networks, thereby establishing a direct link between the molecular properties of branched polymers and macroscopic flow properties (e.g., viscosity and stress). The proposed combined custom synthesis and molecular imaging approach will allow for the guided design of polymeric materials with tailored properties that give rise to a desired processing response. In this way, the proposed work will provide crucial insight into the improved processing and manufacturing of branched polymers. The proposed work also integrates cutting-edge research in molecular rheology with the educational training of graduate and undergraduate students, which is accomplished by mentoring students to work in a collaborative workspace. Educational outreach will be incorporated by working with the Illinois iRise program, which actively engages local K-12 high school science teachers in the Urbana-Champaign area to develop experimental labs for the classroom, and mentors middle and high school students from underrepresented groups, with a particular focus on sparking an interest in science through hands-on experiments. The proposed research also includes participation in the Multicultural Engineering Recruitment for Graduate Education (MERGE) program at the University of Illinois, which aims to recruit students from underrepresented groups in engineering.