A Fundamental Review of the Relationships between Nanotechnology and Lignocellulosic Biomass - The Nanoscience and Technology of Renewable Biomaterials - page 29

and (3) a knowledge base which relates these interactions to more applied areas
of adsorption/desorption, drying, dimensional stability strength/weight relationships,
surface modification, product durability, and process improvements. The majority of the
work considered to be precompetitive would include fundamental studies that relate to
fiber/water or other lignocellulose/water interactions. These would relate to areas such
as the impact of the nanostructure and properties such as the degree of crystallinity,
dimensions of microfibrils and microfibril angle. The surface chemistry and topography
of these materials at interfaces between water and the lignocellulosics at the nanoscale
will have a big impact on how the materials respond to moisture. Heats of immersion
or wetting, energies of adsorption of vapor, and surface free energy of the materials
are all impacted by the natural nanostructures. In addition to the cellulose portion
itself, hemicelluloses, lignin, extractives and trace minerals etc. will also influence the
response of these materials to water or water vapor. Fundamental studies characterizing
these materials based on surface science would provide a base to move into applications
that take advantage of the properties at the nanoscale.

1.12.4 Producing Hyperperformance Nanocomposites from Nanocrystalline

Cellulose

In addition to the wood-based composites, paper and paperboard can be considered
to be a form of nanocomposite as they are made up of components that are essentially
nanodimensional. Most work, to date, has been the result of empirical formulation where
wood or pulp fibers have been mixed together with other components to make useful
functional materials. Cellulose is a material which has unique tensile properties. In its
pure form it can create fibers that are as strong or stronger then Kelvar (Cellulose =

70 to 137 GPa, Kevlar 100 GPa). It is desired to form composites in which cellulose

provides its maximum tensile strength. Other properties of interest include formability
and geometrical complexity at very small scale, unique physical properties, surface
smoothness, biomedical compatibility, and ability to reinforce polymer foams.
It is also desired though the use of nanomaterials, and chemistry to either form or
reform cellulose fibers in a variety of matrixes in which the cellulose can contribute
its full modular strength to the matrix (Podsiadlo 2007). It has been postulated that
the structure of wood is the result of the cellulose nanofibrils forming liquid crystal
arrays under the influence of the hemicellulose (Vincent 2002). This represents a form
of self-assembly that we would like to capture in order to produce new materials with
high strength at lightweight. The interactions are typically noncovalent, such as hydro-
gen bonding and Van der Waals forces but, because of the extremely small size the
interactions add up to provide a high degree of strength.
Other potential avenues can also be investigated to accomplish this. These include:
(1) modification of the side chains of inorganic compounds, such as siloxanes, silanes,
or sodium silicates to link the cellulose fibers through Si-OH bonds forming an organic/
inorganic matrix; (2) growing the cellulose from bacteria; or an enzyme engine such
that the cellulose forms in a matrix; (3) a nanostructure template and nanocatalysts
could be used to help structure the matrix and increase the rate of formation of the
cellulose fibers within the structured matrix; (4) disassembly of plants with enzymes/

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