Correlating Fluctuations of Individual Monomers with Morphology and Mechanical Properties of Heterogeneous Gels

NON-TECHNICAL SUMMARY:

This project will advance our understanding of polymer gels, an economically important class of materials that consist mostly of liquid but are held together by a sparse mesh of long polymer molecules. Gels are important to health applications, where they are used in medical treatments such as wound dressings and drug delivery systems that gradually release medicines.

They are also used in a variety of industries, ranging from food and personal care commodities, to defense and infrastructure, where they find use as sealants, adhesives and flame retardants. This project will advance our understanding of polymer gels by measuring how variations at the molecular level determine their mechanical properties, e.g. how resistant these materials are to being squeezed and stretched, properties that are central to their many uses.

The accompanying educational and outreach efforts seek to broaden the pipeline of STEM scientists and engineers by (i) introducing young learners at the K-8 level to molecules via playful learning environments on mobile phones, (ii) increasing awareness of materials engineering as a discipline amongst pre-college students through hands-on learning workshops, and (iii) supporting undergraduate research projects.

TECHNICAL SUMMARY:

This research will contribute knowledge to the ongoing, now multidecadal, endeavor of establishing a complete mechanistic understanding of the mechanical behavior of polymer gels. The objective is to establish the correlation between spatiotemporal fluctuations of individual monomers and network junction points with the morphology and macroscopic elastic properties of the parent gel networks, which are invariably heterogeneous.

The timeliness of the research arises from recent advances in super-resolution optical microscopy that allow for the tracking of single molecules with unprecedented spatiotemporal resolutions and the imaging of gel morphology on the nano and sub-micron scale. Gels which exhibit inhomogeneous distributions of monomer density, commonly known as spatial heterogeneities, will be studied by (i) quantifying spatiotemporal fluctuations with single monomer fidelity in gels that are prepared across a variety of thermodynamic conditions, and (ii) correlating variations in spatiotemporal fluctuations of monomers across nano and sub-micron scale morphological features with the macroscopic bulk modulus of the respective gels.

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.