This work presents new nano-composites possessing multiple interesting properties: strength, transparency, self-healing and biodegradability. Nature makes multi-property materials that gain their strength and functionality from the precise assembly of hard anisotropic particles embedded in a soft matrix. Despite intense research in the last years, the production of low defect bio-inspired nanostructures leading to composites with complex properties is still a challenge. Layer-by-layer (LbL) assembly pioneered and developed by our team since the early 90's allows the construction of hybrid architectures with controlled nanoscale composition and architecture. We used LbL assembly to prepare micron thick wood-inspired films using microfibrillated cellulose (MFC) and polyvinylamine (PVAm). In these transparent nano-structured films the in-plane orientation of cellulose fibers yields materials whose Young's modulus and strength surpass those of spruce, the wood from which MFC is produced. We will discuss how the deposition parameters control the layer growth (from 9 to 55 nm per layer pair), the composition, and the mechanical properties of the nano-composite films. Experiments on the plasticizing effect of water also evidenced that hydration can turn a strong and brittle film (Young's modulus of 16Gpa) into a soft and ductile material (Young's modulus of 0.1GPa) and enable self-repair.(A) Mechanical properties of some cellulose based materials. (B) Photograph of a 3.8�m thick synthetic wood film, edges are outlined for clarity.

Transparent and ultrastrong synthetic wood through bio-inspired LbL assembly

248th National Meeting (2014)

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