CAREER: Molecular Rheology of Architecturally Complex Polymers

1254340 SchroederPolymers是从消费产品到电子产品等无数技术的基础。尽管最近在该领域取得了进展，但对缠结聚合物溶液的流动性质缺乏充分的了解。聚合物加工中的主要挑战来自支化聚合物的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，本体流变学方法已被用于研究聚合物流动，但这些方法平均了单个分子的运动。为了克服这些挑战，需要一种新的分子探针动力学方法。拟议的研究的目的是提供一个分子水平的观点支化聚合物动力学流动使用单分子方法。将研究缠结梳状聚合物的聚合物应力松弛和非线性流动特性，并将实验获得的单一聚合物数据与理论模型进行比较。以这种方式，将追求在分子水平上直接观察主链和分支弛豫，通过在主链和侧链分支上使用双色荧光染料来促进。拟议的研究依赖于PI实验室开发的三项创新技术：（1）定制合成具有与合成链类似的性质的线性和支链单链DNA（ssDNA）聚合物，（2）在结构特异性位置（例如主链和分支）处的支链ssDNA聚合物的双色标记，以及（3）允许受控流体流动的基于微流体的自动化流动系统，结合具有纳米级分辨率的聚合物构象的单分子成像。更广泛的影响。这项研究将提供纠缠拓扑网络的详细分子水平视图，从而在支化聚合物的分子性质和宏观流动性质（例如，粘度和应力）。所提出的组合定制合成和分子成像方法将允许具有定制特性的聚合物材料的引导设计，所述定制特性产生期望的处理响应。通过这种方式，所提出的工作将为改进支化聚合物的加工和制造提供重要的见解。拟议的工作还将分子流变学的前沿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。教育推广将通过与伊利诺伊州iRise计划，积极参与当地K-12高中科学教师在厄巴纳-香槟地区开发实验室的教室，并辅导初中和高中学生从代表性不足的群体，特别注重通过动手实验引发对科学的兴趣。拟议的研究还包括参与伊利诺伊大学的多元文化工程研究生教育招聘（MERGE）计划，该计划旨在从工程领域代表性不足的群体中招募学生。

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.