CAREER: Connecting the Wetting and Rheological Behaviors of Polymer Grafted Nanoparticles in Polymer Melts

美国国家科学基金会-化学与运输系统分部-颗粒与多相过程项目（1415）摘要申请号：0644890首席研究员：Green， David l .隶属于：弗吉尼亚大学主校区申请题目：职业生涯：聚合物熔体中聚合物接枝纳米颗粒的润湿和流变行为的联系在纳米颗粒表面接枝聚合物刷的最新进展，允许广泛的先进聚合物纳米复合材料的配方，其中刷的作用是防止颗粒聚集。通过最近nsf支持的研究，PI是第一个从根本上将刷的润湿与纳米颗粒的均匀分散联系起来的人之一，用于PDMS熔体中聚二甲基硅氧烷（PDMS）接枝二氧化硅纳米球的模型系统。在该研究中，pdms接枝的纳米颗粒是通过一种既定的“接枝”方法制成的，这种方法需要预先形成的聚合物链的共价连接直接连接到纳米颗粒表面。“接枝”方法可以研究低至中等PDMS接枝密度对纳米颗粒分散的影响。该研究将采用原子转移自由基聚合（ATRP），一种最近发展起来的“接枝”方法，从单分散二氧化硅纳米颗粒的表面，一个单体一个单体地构建聚苯乙烯（PS）和聚甲基丙烯酸甲酯（PMMA）刷。与“接枝到”方法相比，“接枝从”技术允许在更大的接枝密度范围内合成聚合物刷。最终，这组实验将产生系统的数据，这些数据将允许量化纳米颗粒之间的吸引力强度以及控制凝胶过程的相关时间和长度尺度。更广泛的影响：更广泛的影响有三个方面。首先，自洽模型与实验数据的校准将允许预测物理性质，如粒子间距，然后可用于优化一系列材料性质。其次，设计良好的模型系统将允许物理学家、胶体科学家和流变学家研究和量化凝胶现象，以促进在广泛的实验室中实验数据的比较。第三，提出的研究为实现教育和推广目标提供了一个很好的媒介，让更多的学生接触到科学和工程的职业生涯。为此，PI将为一个暑期项目寻求资金，让中学教师在他的实验室里接触尖端研究，创建演示，向学生介绍纳米粒子的迷人特性，并利用本科生研究经验项目，为弗吉尼亚大学工程研究生的未被充分代表的学生建立一个管道。通过将这些项目定位于特定的地理区域和人口，PI希望增加化学工程领域女性和少数族裔博士的数量。

National Science Foundation - Division of Chemical &Transport Systems Particulate & Multiphase Processes Program (1415)ABSTRACTProposal Number: 0644890Principal Investigator: Green, David L.Affiliation: University of Virginia Main CampusProposal Title: CAREER: Connecting the Wetting and Rheological Behaviors of Polymer Grafted Nanoparticles in Polymer MeltsIntellectual Merit: Recent advances in grafting polymer brushes to nanoparticles surfaces permit the formulation of a wide range of advanced polymer nanocomposites in which the brush serves to prevent particle aggregation. Through recent NSF-supported research, the PI was one of the first to fundamentally connect the wetting of the brush to the uniform dispersion of nanoparticles for a model system of polydimethylsiloxane (PDMS)-grafted silica nanospheres in PDMS melts. The PDMS-grafted nanoparticles in that study were formulated by an established "grafting to" method that entailed the covalent attachment of pre-formed polymer chains directly to the nanoparticle surface. The "grafting to" method enabled the study of the impact of low-to-moderate PDMS graft densities on nanoparticleDispersion. The research will to employ atom transfer radical polymerization (ATRP), a recently developed "grafting from" methodology, to construct polystyrene (PS) and polymethylmethacrylate (PMMA) brushes monomer-by-monomer from the surface of monodisperse silica nanoparticles. The "grafting from" technique permits the synthesis of polymer brushes over a wider range of graft densities than the "grafting to" method. Ultimately, this set of experiments will produce systematic data that will permit quantification of the strength of attraction between nanoparticles as well as the relevant time- and length-scales that control the gelation process.Broader Impacts: Broader impacts are three-fold. First, the calibration of self-consistent models to experimental data will permit the prediction of physical properties such as the interparticle spacing that could then be used to optimize a range of materials properties. Second, formulation of well-designed model systems will permit physicists, colloidal scientists, and rheologists to study and quantify gelation phenomena to facilitate comparisons of experimental data across of wide range of laboratories. Third, the proposed research provides an excellent medium for achieving the educational and outreach goal of exposing more students to a career in science and engineering. To this end, the PI will seek funds for a summer program to expose secondary school teachers to cutting-edge research in his lab, create demonstrations to introduce students to the fascinating properties of nanoparticles, and utilize the Research Experience for Undergraduates program to establish a pipeline of underrepresented students for engineering graduate study at the University of Virginia. By targeting these programs to specific geographic areas and populations, the PI hopes to increase the number of woman and minority PhDs in chemical engineering.