CAREER: Molecular Rheology of Architecturally Complex Polymers

从消费产品到电子产品，聚合物是无数技术的基础。尽管该领域最近取得了进展，但对纠缠聚合物溶液的流动特性仍缺乏充分的了解。聚合物加工中的一个主要挑战来自于支链聚合物异常复杂的流动动力学，其中分子拓扑结构最终决定了宏观材料响应。传统上，体流变学方法被用于研究聚合物流动，但这些方法平均掉了单个分子的运动。为了克服这些挑战，需要一种新的分子方法来研究探针动力学。知识价值。本研究旨在利用单分子方法从分子水平上研究支化聚合物的流动动力学。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，并将从实验中获得的单聚合物数据与理论模型进行比较。这样，就可以在分子水平上直接观察到主链和支链的弛豫，通过在主链和侧链分支上使用双色荧光染料来实现。拟议的研究依赖于PI实验室开发的三种创新技术：(1)定制合成具有类似合成链性质的线性和支链单链DNA （ssDNA）聚合物，(2)在结构特定位置（如骨干和分支）对支链单链DNA聚合物进行双色标记，以及(3)基于微流体的自动化流动系统，该系统允许控制流体流动，并结合纳米级分辨率的聚合物构象单分子成像。更广泛的影响。本研究将提供纠缠拓扑网络的详细分子水平视图，从而在支链聚合物的分子特性和宏观流动特性（例如粘度和应力）之间建立直接联系。所提出的结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指导设计，从而产生所需的处理响应。通过这种方式，提出的工作将为改进支化聚合物的加工和制造提供关键的见解。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结合起来，通过指导学生在协作工作空间中工作来完成。通过与伊利诺伊州iRise项目合作，教育推广将被纳入其中，该项目积极吸引厄巴纳-香槟地区当地K-12高中科学教师为课堂开发实验实验室，并指导来自代表性不足群体的初高中学生，特别注重通过动手实验激发对科学的兴趣。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.