Cellulose nanocrystals (CNCs) are an exciting filler for emerging bio-renewable nanocomposite systems. CNCs provide mechanical reinforcement through the development of a strong hydrogen bonding network within the matrix, when loaded above a critical percolation threshold, greatly enhancing the storage modulus. Upon the introduction of water, competing interactions consume hydrogen bonding sites thereby reducing the mechanical reinforcement provided by CNCs.<br/><br/>We explore the dynamics of the mechanical softening upon exposure to water, focusing on the role of CNC-water interactions on water transport in nanocomposites. Additionally, we provide insight into this process through a relationship between storage modulus and water diffusion as functions of filler loading. Dynamic mechanical analysis (DMA) coupled with a relative humidity accessory enabled direct evaluation of the mechanical adaptivity in response to the water stimulus and thermogravimetric analysis – sorption analysis (TGA-SA) was implemented to evaluate the diffusivity of water in a high relative humidity environment. Following a hindered diffusion model, the ratio of bound-unbound water was characterized for its impact on mechanical softening providing new insight into the softening kinetics. Finally, local water transport was evaluated through Fourier transform infrared – attenuated total reflectance (FTIR-ATR) spectroscopy and compared to bulk transport phenomenon.

Diffusion-softening of a mechanically adaptive cellulose nanocrystal polyurethane composite

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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