Stratification of layer-by-layer (LbL) polyelectrolyte films lies in the heart of advanced biomedical and optical applications of polyelectrolyte multilayer (PEM) films, yet is often compromised by molecular diffusion and intermixing. In this project, fundamental correlations between dynamics of polymer chains and internal structure of PEMs will be explored, and this knowledge will be applied to develop strategies for the construction of stratified LbL PEM films and to study evolution of their structure during aging. Specifically, inter-chain dynamics will be explored in three cases: (1) in solution; (2) between solution and the films during multilayer construction; and (3) at a post-assembly step during aging of LBL films in humid or aqueous environments. Fluorescence correlation spectroscopy (FCS), a combination of FCS and in situ ATR-FTIR, and a combination of fluorescence recovery after pattern photobleaching (FRAPP) and neutron reflectivity (NR) will be applied for cases (1)- (3), respectively. The project involves synthesis of well-defined polybase-polyacid (PB-PA) pairs associated through ionic pairing or hydrogen-bonding. The central suggestion is that translational diffusion of polymers within PEMs is anisotropic, and proposed experiments aim to reveal the degree of this anisotropy as well as how this anisotropy evolves with time when PEM films are aged in high humidity environment or in aqueous solutions under varying temperature and/or ionic strength. The knowledge generated in this proposal can be used to predict interactions, motions, relaxations and order in a broad range of PEM films.
NON-TECHNICAL SUMMARY:
This project provides knowledge of dynamics and structure of self-assembled polymer films, which will enable construction and prediction of aging of stratified polymer films for biomedical and optical applications. One example includes polymer coatings enabling sequential delivery of therapeutic compounds from the surface of a biomedical device or an implant. Importantly, this project will create a fertile training ground for the participating graduate students and summer undergraduate students in forefront issues of polymer science, a training ground further enriched by collaboration with NIST and ORNL. A new course on nanostructured polymers will be developed as part of the highly interdisciplinary Stevens Nanotechnology Graduate Program. A significant part of the project includes working with high school students from the Northern New Jersey area and disseminating knowledge through experimental demonstrations and poster exhibition involving K-12 high school students. Through existing close links with the K-12 ACS SEED and the Partners in Science Program NJ program, a new educational initiative will be developed. Specifically, by working with a recently started NSF-funded GK-12 initiative, New Jersey Alliance for Engineering Education (NJAEE), and with the Stevens Center for Innovation in Engineering and Science Education (CIESE), a teaching module Polymers in Our Life will be built and piloted in a high school setting. The module will be featured on the NJAEE website, and linked to the CIESE website, which enjoys hundreds of thousands of site visits by K-12 educators and students each year.
