CAREER: Polymer Absorption and Transport in Nanopores

这份职业计划的目标是在分子水平上了解和控制聚合物在纳米孔中的吸附和传输，并阐明这些过程与平面上的过程有何不同。这些研究尤其涉及到高效液相色谱(HPLC)中的聚合物分离、聚烯烃和加氢催化中的纳米孔载体设计，以及纳米流体通道中的大分子操纵。这一建议旨在弥合高效液相分析中聚合物吸附和分离之间的现有知识差距。特别是，与从主体溶液到纳米孔开口的链转移以及随后在纳米孔中的传输和吸附相关的传输限制的关键作用仍然知之甚少。为了更好地理解这些现象，我们将研究聚合物在纳米多孔二氧化硅颗粒中的吸附，并将结果与氧化铝(AAO)膜中受控良好的纳米孔通道结构中的聚合物传输进行比较。此外，电子显微镜将被用来直接研究聚合物在这种纳米孔衬底上的形态。我们的初步结果促使我们将拟议的研究集中在四个特定目标上：(1)研究纳米孔尺寸对聚合物吸附的层析[即连续]和批处理条件的作用；(2)检测纳米孔口吸附的“空间位阻”效应；(3)使用末端功能聚合物和高度不对称的嵌段共聚物了解限制在纳米孔中的末端吸附的聚合物的链“受挫”效应；(4)使用透射电子显微镜和膜渗透压计研究聚合物通过AAO纳米通道膜的链传输。拟议的研究将使研究纳米孔中的表面结合聚合物成为可能，并将有助于理解聚合物链是如何从口腔扩散到孔中的，特别是在与链的大小相比较小的孔中。这项研究将对新的聚合物高效液相色谱技术的发展产生广泛的影响，这些技术可以补充现有的尺寸排除层析技术。将开发一个名为“虚拟聚合物实验室”(VPL)的教育网站，提供与聚合物和普通化学有关的多媒体教育资源。为了对各级教育产生影响，VPL网站将通过与(A)特洛伊初级博物馆；(B)当地高中和(C)仅限本科生的大学建立合作伙伴关系，利用以下途径进一步改进：(I)为特洛伊初级博物馆开发一个“关于高分子的动手科学家庭计划”，特别针对K-6儿童及其家长(Ii)改进“将纳米技术带到课堂”，这是位于RPI的NSF纳米科学和工程中心的一个现有计划(Iii)设计关于聚合物的高效液相色谱客座讲座，专门针对本科生。为了吸引学生，除了我的基于接触的活动，教育计划将进一步演变为基于网络的教育材料，其中包含预先录制的“虚拟”计划演示的多媒体剪辑。研究成果将被用于改善聚合物教学，使本科生和研究生都能接触到涉及聚合物吸附、高效液相色谱和显微镜的跨学科研究。

The goal of this CAREER proposal is to understand and control polymer adsorption and transport in nanopores at a molecular level and to elucidate how these processes differ from those on flat surfaces. These studies are particularly relevant to applications involving polymer separation in high performance liquid chromatography (HPLC), nanoporous support design in polyolefin and hydrogenation catalysis, and manipulation of macromolecules in nanofluidic channels. This proposal aims to bridge the existing knowledge gap between polymer adsorption and separation in HPLC analysis. In particular, the critical role of transport limitations associated with the chain transfer from a bulk solution to the nanopore opening, and the subsequent transport and adsorption in nanopores remains poorly understood. To achieve a better understanding of these phenomena, polymer adsorption will be studied in nanoporous silica particles containing well-defined tortuous pores of high specific surface areas and the results will be compared with polymer transport inside well-controlled nanopore channel architectures present in anodized aluminum oxide (AAO) membranes. In addition, electron microscopy will be applied to directly study the morphology of polymers in such nanoporous substrates. Our preliminary results motivate us to focus the proposed research into four specific objectives: (1) Studying the role of nanopore size on the chromatographic [i.e., continuous] and batch conditions for polymer adsorption; (2) Examining "steric crowding" effects at the pore mouth for adsorption in nanoporous silica; (3) Understanding chain "frustration" effects of terminally-adsorbed polymers confined in nanopores using end-functional polymers and highly asymmetric block copolymers; and (4) Investigating polymer chain transport through AAO nanochannel membranes using TEM and membrane osmometry. The proposed research will enable investigation of surface-bound polymers in nanopores and will help to understand how polymer chains diffuse into the pores from the mouth, especially in pores that are small compared to the size of the chains. The proposed research will have a broad impact on the development of novel polymer HPLC techniques, which can complement existing size exclusion chromatography techniques. An educational website called "Virtual Polymer Laboratory" (VPL) will be developed to provide multimedia educational resources related to polymers and general chemistry. To impact education at all levels, the VPL website will be further improved by establishing partnerships with (a) the Troy Junior Museum; (b) local high schools and (c) undergraduate-only colleges using the following avenues: (i) Developing a "Hands-on Science Family Program on Macromolecules" for the Troy Junior Museum, particularly targeted towards K-6 kids and their parents (ii) Improving "Bringing Nanotechnology to the Classroom", an existing program in the NSF Nanoscale Science and Engineering Center at RPI (iii) Designing guest lectures on polymer HPLC, specifically for undergraduates. To attract students beyond my contact-based activities, the educational program will be further evolved into web-based educational materials containing multimedia clips of pre-recorded "virtual" program demonstrations. The research results will be employed to improve polymer education, by exposing both undergraduate and graduate students to cross-disciplinary research involving polymer adsorption, HPLC and microscopy.