Cellulose, as the most abundant polymer on earth, is a promising feedstock for the growing research in sustainable materials development. Cellulose nanofibrils (CNFs), derived from woody biomass by mechanical refinement, are already widely utilized industrially due to their low cost, wide availability, and competitive material properties relative to other biomaterials. Not only can cellulose be used independently, but it can also be used in conjunction with polymer matrices to replace non-biodegradable reinforcements in bioplastics, such as carbon and aramid fibers. However, when compounded into polylactic acid (PLA) based composites, unmodified CNFs aggregate, weakening the material. This aggregation can be mediated by disrupting the hydrogen bonding of the hydroxyl groups by polymerizing monomers from a reactive handle using a grafting-through approach. This project set out to determine the optimal conditions for the polymerization of styrene on methacrylated CNFs (metCNFs) for improved mechanical properties of cellulose-reinforced PLA. First, styrene was polymerized onto metCNF using an aqueous emulsion polymerization with potassium persulfate as the radical initiator. The relative concentrations of styrene, cellulose, and the initiator were varied. The success of the polymerizations was determined using quantitative FTIR spectroscopy, comparing polystyrene-associated band heights. SEM was used to analyze the impact of each variation on the fibrillar morphology of the nanofibrils. To understand the impact of the polymerization parameters on grafted chain length and micelle size, size-exclusion chromatography and dynamic light scattering were employed. Finally, the styrene-polymerized metCNFs were compounded into PLA, and the maximum stress and modulus were used determine the viability of the styrene-polymerized metCNFs as PLA reinforcements.

Modification of cellulose nanofibrils with polystyrene for composite production via grafting-through emulsion polymerization

ACS Spring 2022

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