Nature uses nanocomposites for a wide range of applications. Inspired by this we have been interested in how cellulose nanocrystal (CNC) composites can be used to access a range of nanocomposites that mimic the basic architecture and function of natural biosystems. For example, we have been investigating the use of CNCs to access mechanically-dynamic nanocomposites that have been inspired by the inner dermis of the sea cucumber and the squid beak. 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 shown that CNCs (from a range of different biosources such as tunicates, cotton and microcrystalline cellulose) embedded within a variety of polymer matrices show mechanical switching (stiff to soft) 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. More recently, we have shown that is possible to reprogram this response by grafting lower critical solution polymers on the CNCs to yield composites that start soft and become stiff upon insertion to water at body temperature. Our latest results on using CNCs to access bioinspired nanocomposites will be discussed.

Bio-inspired nanocomposites

256th National Meeting (2018)

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