SusChEM: Pro-Active Networks from Degradable Acetals (PANDAs) via Thiol-ene Photopolymerization

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Synthetic polymers are typically resistant to degradation and far outlive the useful lifetime of the use for which they are designed - a problem that results in the accumulation of plastics in landfills and oceans. Even upon degradation, the byproducts of plastics are sometimes toxic and serve no useful or active purpose in the environment. The Macromolecular, Supramolecular, and Nanochemistry (MSN) program of NSF Chemistry Division supports the efforts of Professors Patton and Mavrodi at the University of Southern Mississippi to advance the design of degradable polymers. Essential oil derivatives are used as primary building blocks of the polymers. The materials are designed to undergo complete degradation under mild conditions resulting in regeneration of essential oils. Stemming from the broad-spectrum antimicrobial and antifungal activity observed for many essential oil constituents, these degradable materials are potentially useful for a range of pharmaceutical, biomedical, and agricultural applications. The researchers have established active outreach programs to local K-12 schools including the ?What is a Polymer? program (impacting 500 students annually) and the ?Discover Nature? summer science camp. A new outreach initiative and collaboration with the local 3D (Dynamic Dyslexia Design) School is initiated. ?Science Nights @ 3D? engage dyslexic students (and their families) with hands-on activities that require visual, kinesthetic, and auditory processing while introducing fundamental, grade appropriate science and math concepts.The overarching goal of this project is the design, synthesis, and characterization of degradable polymer thermosets called "pro-active networks from degradable acetals (PANDAs)" via thiol-ene photopolymerization. The approach is rooted in the design of multifunctional acyclic and cyclic acetal monomers derived from essential oil precursors that enable control over network chemistry and network structure for tunable degradation profiles. PANDAs covalently incorporate aldehydes (e.g., vanillin, anisaldehyde, citronellal) and phenolic compounds (carvacrol, thymol) derived from essential oils directly into the polymer network via an acetal linkage - either as pendant groups (cyclic acetal) or as an integral part of the polymer backbone (acyclic acetal). Exposure to conditions conducive to acetal degradation (e.g., change in humidity/pH) regenerates the essential oil building blocks. Degradation profiles are determined to ascertain the erosion mechanism (surface vs. bulk) and aldehyde/phenol release kinetics, and to correlate degradation/release profiles with chemical and physical properties of the polymer network (e.g., hydrophobicity and crosslink density). The project actively trains a diverse group of graduate and undergraduate students in an interdisciplinary research environment and engages local K-12 schools, in outreach. This includes a collaboration with the local Dynamic Dyslexia Design (3D) School.