Due to their flexibility, low density and recyclability, polymer films and coatings are playing an increasingly important role in the regulation of gas transport in a wide range of applications such as gas barriers for food, beverage, microelectronics and medical device packaging. Adding nanoparticles and/or blending multiple polymers together have proven to be effective methods to tune gas transport properties of nanocomposite films. Adding high concentrations of nanoparticles, in particular, is a powerful approach for producing high performance gas barriers and gas separation membranes. In this work the investigators will produce polymer films with high nanoparticle loadings via solvent-driven infiltration of polymers (SIP) into layers of nanoparticles. In this process, layers of nanoparticles, sitting on top of a polymer layer, are filled with a solvent. Some of this solvent moves into the polymer layer and softens or plasticizes, the polymer material. Once the polymer is plasticized, it can move into the nanoparticle layer, filling in the gaps between nanoparticles, by attractive interactions with either the solvent or the nanoparticles. The investigators will study which of these interactions are most important for polymer infiltration and how to tune these interactions to obtain polymer films with high loadings of nanoparticles. These hard, solid nanoparticles maintain barriers which limit polymer's ability to expand. These constrained polymers are expected to exhibit improved gas barrier properties, making them attractive for various packaging applications.
The investigators hypothesize the dynamics and thermodynamics of polymer chains in the interstices of nanoparticle packings under extreme nanoconfinement will be dominated by the thermodynamics of the interfaces. Solvent-infiltration of polymers (SIP) provides an ideal platform to characterize the dynamics and thermodynamics of confined polymers and transport of gas molecules through a binary polymer phase under extreme nanoconfinement. This work will lead to fundamental understandings of how polymer-solvent-nanoparticle interactions affect the infiltration mechanism and dynamics, as well as the thermodynamics of polymers under extreme nanoconfinement. The dynamics and resulting structure of SIP will be studied using in situ spectroscopic ellipsometry as well as molecular dynamics (MD) simulations. Efficient field-theoretic simulations, including self-consistent field theory, will be used to understand the thermodynamics in the packings and guide both the experiments and MD simulations. The structure-transport property relationship of SIP nanocomposites for different polymer molecular weight and polymer-nanoparticle interactions will be established by characterizing the structure using transmission electron microscopy, MD, and by testing the transport properties through quartz crystal microbalance with dissipation. Because theoretical frameworks to predict the dynamics and thermodynamics of SIP are not currently available, whenever possible, computation-based approaches will provide important guidelines for experimental conditions. The investigators will support involvement from underrepresented minority students by leading cooperative efforts with University of Puerto Rico-Humacao, Advancing Women in Engineering and Louise-Stoke Alliance for Minority Participation and Rachleff Scholars Program. The PIs also plan to develop educational programs and exhibits that showcase the nanocomposites with ultra-high loadings of natural nanomaterials with the help of undergraduate/graduate students for use during outreach activities organized through local high schools and science cafe events.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
