This is an illustration of a single cellulose nanocrystal and a cross-section. Credit: Robert Sinko
Theoretically, nanocellulose could be the next hot supermaterial. A new computational approach allows researchers to design cellulose nanocomposites with optimal properties. A class of biomaterials in many natural systems like trees, cellulose nanocrystals have captured researchers’ attention for their extreme strength, toughness, light weight, and elasticity. The materials are so strong and tough, in fact, that many people think they could replace Kevlar in ballistic vests and combat helmets for military. Unlike their source material (wood), cellulose nanocrystals are transparent, making them exciting candidates for protective eyewear, windows, or displays.
Although there is a lot of excitement around the idea of nanocellulose-based materials, the reality often falls flat.
“It’s difficult to make these theoretical properties materialize in experiments,” said Northwestern Engineering’s Sinan Keten.
Keten and his team are bringing the world one step closer to a materials-by-design approach toward developing nanocomposites with cellulose. They have developed a novel, multi-scale computational framework that explains why these experiments do not produce the ideal material and proposes solutions for fixing these shortcomings, specifically by modifying the surface chemistry of cellulose nanocrystals to achieve greater hydrogen bonding with polymers.
Found in cellular walls of wood, cellulose nanocrystals are an ideal candidate for polymer nanocomposites – materials where a synthetic polymer matrix is embedded with nanoscale filler particles. Nanocomposites are commonly made synthetic fillers, such as silica, clay, or carbon black, and are used in a myriad of applications ranging from tires to biomaterials.
“Cellulose nanocrystals are an attractive alternative because they are naturally bioavailable, renewable, nontoxic, and relatively inexpensive,” Keten said. “And they can be easily extracted from wood pulp byproducts from the paper industry.”
Problems arise, however, when researchers try to combine the nanocellulose filler particles with the polymer matrix. Keten’s solution improves this understanding by focusing on the length scales of the materials rather than the nature of the materials themselves…” we instead strategically tune design parameters in order to develop materials with a targeted property in mind,” Sinko said. “When you are equalizing music, you can turn knobs to adjust the bass, treble, etc. to produce a desired sound. In materials-by-design, we similarly can ‘turn the knobs’ of specific parameters to adjust the resulting properties.” http://www.mccormick.northwestern.edu/news/articles/2015/10/nanocellulose-materials-by-design.html
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