Cellulose nanocrystals (CNCs) have attracted attention in recent years as potential green reinforcing fillers for polymer nanocomposites. A key aspect of these materials are the interactions between the CNC and matrix polymer and as well as between the CNCs themselves. We have recently shown that sulfonated CNCs (from a range of different biosources such as tunicates, cotton and microcrystalline cellulose) embedded within a variety of polymer matrices (including poly(vinyl acetate),polyacrylates, poly(ethylene oxide-co-epichlorohydrin), polybutadiene, styrene-butadiene rubber and polyurethane) show mechanical switching upon exposure to water. It is proposed that in the dry state hydrogen bonding interactions between adjacent CNCs play a role in this reinforcing network, transferring mechanical stresses across the sample, and resulting in stiff materials. Once the water diffuses into the nanocomposite, it competitively hydrogen bonds to the CNC surfaces disrupting the stress-bearing CNC scaffold and softening the nanocomposite. We are currently investigating these mechanically-adaptable nanocomposites as the basis of biocompatible intracortical electrodes, which are stiff to allow facile insertion into the brain and soften after implantation to minimize the bioresponse. This presentation will focus on our latest results on these systems.

Mechanically dynamic composites as biocompatible implants

248th National Meeting (2014)

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