CAREER: Polymer Absorption and Transport in Nanopores

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

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.