(267a) Layer-by-Layer Assembly of Novel Nanocomposites from Cellulose Nanocrystals

Cellulose nanocrystals are emerging as a new class of reinforcing material for the preparation of high performance nanostructured composites. The combination of their natural and renewable origins with exceptional mechanical properties: bending strength °Ö 10 GPa and E °Ö 150 GPa, make them an attractive nanomaterial for the preparation of low cost, light-weight, and ultra-strong hybrid composites for multitude of applications. Unlike carbon nanotubes (CNTs), their exceptional properties (only 6-7 times lower then those of single walled CNTs) are thus far largely unexplored and currently described nanocrystal reinforced composites possess far lower properties then theoretically achievable.

We present here preparation of high-strength thin film composites from 100-300 nm long nanocrystals and poly(diallyldimethylammonium chloride) using layer-by-layer (LBL) electrostatic assembly technique. Assembly and resulting composites were characterized with ellipsometry, UV-vis spectrophotometry, SEM, AFM, and TGA. Mechanical properties were assessed with standard stretching technique by generating stress-strain curves. Unlike previous reports with CNTs, nanocrystals assembly was very fast with as low as 5 seconds required for high density surface coverage. Resulting films possess tensile strength of ¦" = 39 MPa and Young's modulus, Y = 2 GPa. Post-assembly thermal-treatment increases the tensile strength to ¦" = 120 MPa and Y to 2.3 GPa.