THESIS - ROC CH ... - FINAL - resubmission.pdf - University of Guelph

onding between hydroxyl groups and oxygen atoms of adjacent molecules (Moon et al. 2011).
In plants, the parallel stacking of cellulose chains forms the elementary fibrils of the hierarchical
structure. These fibrils, when aggregated in numbers, form larger microfibrils (5-50 nm in
diameter) with crystalline and amorphous regions (Figure 2.1b). The arrangement of these
regions varies between materials and is not yet understood, but it is believed that hydrogen
bonding plays a pivotal role in the formation of complex cellulosic network (Moon et al. 2011).
Due to the many hydrogen bonds between cellulose chains, microfibrils are relatively stable and
have high axial stiffness. These nanofibers tend to have high aspect ratios (µm in length to nm
diameter), and depending on the extraction method and the source material used (wood, ramie,
jute, etc.), aspect ratios will differ. Microfibrils are ideal reinforcement structures and have been
proven to be difficult to solubilize (Eichhorn et al. 2009). Within the cell wall, these microfibrils
are embedded in a gel-like matrix composed of hemicellulose, lignin and pectin polysaccharides
(Wolf-Dieter 1998).
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