CAREER: Polymer Absorption and Transport in Nanopores

本CAREER提案的目标是在分子水平上理解和控制聚合物在纳米孔中的吸附和运输，并阐明这些过程与平面上的过程有何不同。这些研究尤其涉及高性能液相色谱（HPLC）中的聚合物分离、聚烯烃和加氢催化中的纳米孔支撑设计以及纳米流体通道中大分子的操纵等应用。该提案旨在弥合现有的知识差距，高分子吸附和分离的高效液相色谱分析。特别是，与链从体溶液转移到纳米孔开口以及随后在纳米孔中的转移和吸附相关的运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，聚合物吸附将在纳米多孔二氧化硅颗粒中进行研究，纳米多孔二氧化硅颗粒含有明确的高比表面积的弯曲孔隙，并将结果与阳极氧化铝（AAO）膜中存在的控制良好的纳米孔通道结构中的聚合物运输进行比较。此外，电子显微镜将被应用于直接研究聚合物在这种纳米多孔基质中的形态。我们的初步结果激励我们将研究重点放在四个具体目标上：(1)研究纳米孔尺寸对色谱（即连续）和批量聚合物吸附条件的作用；(2)研究纳米孔二氧化硅吸附孔口的“空间拥挤”效应；(3)利用端功能聚合物和高度不对称嵌段共聚物了解纳米孔中末端吸附聚合物的链“挫折”效应；(4)利用透射电镜和膜渗透法研究聚合物链在AAO纳米通道膜中的传输。所提出的研究将有助于研究纳米孔中的表面结合聚合物，并有助于了解聚合物链如何从口腔扩散到孔中，特别是在与链尺寸相比较小的孔中。该研究将对新型聚合物高效液相色谱技术的发展产生广泛的影响，可以补充现有的尺寸排除色谱技术。一个名为“虚拟高分子实验室”（Virtual Polymer Laboratory， VPL）的教育网站将会被开发，提供高分子和一般化学相关的多媒体教育资源。为了影响各级教育，VPL网站将进一步改进，与以下机构建立伙伴关系：(a)特洛伊少年博物馆；(b)当地高中和(c)仅限本科生的大学，采用以下途径：(i)为特洛伊少年博物馆开发“大分子动手科学家庭计划”，特别是针对K-6年级的孩子和他们的父母；（ii）改进“将纳米技术带入课堂”，这是RPI国家科学基金会纳米尺度科学与工程中心的现有计划；（iii）设计专门针对本科生的聚合物HPLC客座讲座。为了吸引学生，我的教学项目将进一步发展为基于网络的教学材料，其中包含预先录制的“虚拟”课程演示的多媒体剪辑。研究成果将用于改善高分子教育，使本科生和研究生接触到涉及高分子吸附、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.