Polymer – Metal-Organic Framework Composites for Defense Against Chemical Warfare Agents
Date
2021
Authors
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Publisher
University of Delaware
Abstract
The continued worldwide use of chemical warfare agents (CWAs) necessitates the development of novel personal protective equipment (PPE). In particular, current PPE suffers from high burden to the user and a lack of ability to detoxify CWAs. Metal-organic frameworks (MOFs) have emerged over the past decade as highly active designer materials for adsorption of and reaction with CWAs. The research in this dissertation focused on methods for incorporation of several archetypal MOFs into polymers for enhanced PPE using ‘MOF-first’ and ‘Polymer-first’ strategies. For ‘MOF-first’ techniques, in which MOFs are synthesized and then incorporated into polymers during processing, film- and fiber-based composites were fabricated to improve reactivity and protection, while reducing the burden, of barriers in comparison to current PPE. Shortcomings of this technique, such as defects at the MOF-polymer interface and MOF particle agglomeration, were overcome using chemical modification (e.g., post-synthetic modification using acyl chlorides) and post-processing (e.g., solvent annealing) techniques. Resulting films from modified MOFs had higher CWA solubility, slower diffusion rates, longer permeation times, and increased detoxification of CWAs, as well as increased moisture vapor transport and better mechanical properties, in comparison to baseline polymers and common protective materials (e.g., latex, nitrile, and butyl rubber gloves). For ‘Polymer-first’ techniques, in which MOFs are grown in situ in pre-processed polymers, research focused on seeding of poly(ethylene oxide), PEO, fibers and films with MOF precursors followed by vapor phase synthesis of MOFs. The addition of Zn salts reduced the hydrodynamic radius of PEO and viscosity, but increased the electrical conductivity, of aqueous solutions and resulted in electrospun nanofibers from which MOFs were synthesized. The fundamental conclusions drawn from the PEO seeding study can be used to make block copolymer and blended films and fibers for enhanced PPE. Overall, the research in this dissertation resulted in novel technologies for PPE as well as new directions for improvements to MOF-polymer composites.
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Keywords
Fiber-based composites, Metal-organic framework, Mixed matrix composites, Personal protective equipment