Building a Platform of Impact-Energy Absorbing Materials: How Molecular Manipulations Translate into Macroscopic Properties

University Of Florida, Gainesville FL

Investigators

Abstract

NON-TECHNICAL SUMMARY: A unique property of polymers is their ability to absorb mechanical energy during impact events by transferring that energy into molecular motions of the individual polymer chains. This project is focused on studying the fundamental materials properties for a platform of energy-absorbing polymers and developing a toolbox to introduce molecular mechanisms to increase toughness, energy dissipation, and the potential for nanoscale self-healing that will increase the lifespan of the material. This platform is based on polymer network materials called "thiol-ene network thermosets". They can be made through chemistry that offers fast reaction times and highly homogeneous networks, like a chain-link fence, resulting in high energy absorption capacity. Previous work in the Savin group has demonstrated the ability to make molecular-level changes in the network and have this translate into macroscopic changes in the physical properties of the materials. These changes can be done in a modular way using facile chemistry. The resulting materials have applications in sound damping, shatterproof coatings, personal protective equipment (e.g., mouthguards and multi-impact foams), and ballistics protection. Advances in scientific discovery will be incorporated into the education and training of students, integrating a broad range of disciplines including chemistry, physics, biochemistry, and polymer science. Group members will gain a comprehensive understanding of polymers in many areas of synthesis, characterization, morphology, scattering and rheology, from both a fundamental and an applied standpoint. This multidisciplinary approach is beneficial not only for education, but also to produce well-rounded graduates who are attractive to a variety of employers in both academic and industrial settings. Diversity and involvement in K-5 elementary science outreach are also strongly emphasized. TECHNICAL SUMMARY: The objective of this research is to study the fundamental materials properties for a platform of energy absorbing polymers based on thiol-ene network (TEN) thermosets. Previous research on TENs has shown the ability to make molecular-level manipulations through chemistry and have this translate to changes in macroscopic performance and function. The goal of this research is to exploit advances in TEN modification to synthesize new monomers where we introduce mechanisms to increase toughness, as well as the potential for self-healing that will ultimately increase the life span of the material. This will be done for both slab (Aim 1) and foam (Aim 2) materials. In the proposed research, we will introduce these molecular-level mechanisms for energy dissipation and toughness through dynamic-covalent sacrificial, mechanochemical linkages, and incorporation of photo-responsive, liquid crystalline azobenzene substituents. Building a toolbox of network modifications will allow us to discover materials that have the potential to transform the field of energy-absorbing materials by expanding functionality. The modified TEN materials platform that will be developed in this proposal is completely modular and can be applied to applications such as personal protective equipment, curable coatings, ballistics protection, dental restoratives, and polymer composite materials. Successful completion of the proposed research will yield a platform of materials with improved impact-energy absorption properties, as well as an understanding of how molecular design and manipulation translates into dynamics and macroscopic function. 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.