(149c) Reducing Moisture Sensitivity of Protein-Based Thermosets through Protein Charge Modification and Melt Polymerization with Hydrophobic Monomers
AIChE Annual Meeting
Monday, November 8, 2021 - 1:10pm to 1:30pm
Here, we investigate the influence of charged protein functional groups on humidity sensitivity, and demonstrate the reduction of water uptake through the copolymerization of modified whey proteins with the hydrophobic n-butyl acrylate. A combination of esterification and acetylation reactions superneutralize the protein by installing uncharged ethyl esters and amide groups onto carboxylic acids and amines respectively. Superneutralization reduced water solubility of the protein, and resulted in a 46% reduction in water absorption at 90% relative humidity, compared to unmodified protein. Incorporation of the charge modified proteins into a copolymer is enabled by the flexible nature of the employed surfactant compatibilization strategy, where a range of ionic surfactants were shown to be effective at compatibilizing the otherwise immiscible protein-monomer mixtures. Subsequent methacrylation allows the protein to be incorporated into protein-polyacrylate network, where the hydrophobic polyacrylate further reduced moisture absorption. The lowered water uptake of superneutralized proteins is reflected in the copolymer mechanical properties, which remain stable across a wider humidity range compared to non-charge modified and supercharged protein copolymers. Structure-property relationships were further studied using Fourier-transform infrared spectroscopy and atomic force microscopy. Overall, this work provides a strategy to address the performance variability of protein-based materials due to changes in humidity.