Cellulose surface modification is reviewed from the standpoint of the importance of interfacial modification for the development of strong cellulose reinforcement (nanowhiskers, wood fiber, or continuous fiber) in thermoplastic matrices. While continuous fiber composites did not require interfacial modification for improvement in mechanical properties, short fiber composites did. Three alternative methods for modification are highlighted: (a) esterification of pulp fibers in a nonswelling solvent produces a composite with covalent links between cellulose I crystals and a thermoplastic ester matrix; (b) reactive processing via steam-explosion of wood in the presence of polyolefins creates a wood fiber with a thermoplastic matrix surface; and (c) "bottom-up"-nanocomposites are created by the self assembly of irreversibly adsorbing amphiphilic polymers or polyelectrolytes onto cellulose surfaces, and alternatively by the layer-by-layer assembly of anionic cellulose nanowhiskers and cationic starch.
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