Poly(lactic acid) (PLA) is one of most widely produced biomass derived and industrially compostable polymers available that is commonly used for food service and additive manufacturing applications. For applications that require more strength and stiffness, PLA can be reinforced with materials such as carbon and glass fibers, but these are not degradable and thus, reduce the sustainability of the resultant composite. Cellulose nanofibrils (CNFs) are a naturally derived biomaterial that can act as a replacement reinforcement, but their high water content as produced cause them to collapse when dried, destroying their nanoscale structure. Furthermore, their surface energy mismatch with PLA cause them to aggregate when mixed, creating an inferior composite. To address these challenges, CNFs were functionalized with poly(methyl methacrylate) (PMMA) in their native suspension by a grafting-through surfactant free emulsion polymerization. To enable this grafting-through polymerization, the CNFs were first functionalized with a methacrylate group in their native aqueous suspension. During the subsequent surfactant free emulsion polymerization, this reactive handle captured propagating PMMA chains to coat the CNFs. Polymerization conditions could be varied to control the amount of PMMA and the length of polymer chains attached to the surface. These polymer brush modified CNFs could be dried under vacuum without significant collapse of the nanostructure, retaining the nanofibril structure. Changes to polymerization conditions generated a library of materials that were melt compounded with PLA to generate composites with up to 20% increase in strength over the original polymer.

Surfactant free emulsion polymerization to create polymer brush modified cellulose nanofibril reinforcements for poly(lactic acid)

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.