Nanocellulose esterification

Figure 9.2 Surface modification chemistries of nanocellulose for PLA/nanocellulose biocomposites, a, Acetylation b, Esterification with various organic acids c, d, e, Grafting of PCL, PLA, P(CL-fi-LA) f, Silanization g, Silylation h, Carbojymethylation combined with hexanoation i, PEG grafting j, Modified with polyhedral oligomeric silsesquioxane (POSS).

Treating cellulose fibers with sulfuric acid involves esterification of hydroxyl groups by sulfate ions (Yao, 1999). Introduction of sulfate groups along the surface of the crystallites will result in a negative charge of the surface. This anionic stabilization via the attraction/repulsion forces of the electrical double layers at the crystallites is probably the reason for the stability of the colloidal suspensions of flie crystallites (Marchessault et al., 1961). The stable aqueous nanocellulose suspension is shown in Figure 1.1(a). 

Esterification, etherification, silylation and pofymer grafting are regarded as methods of covalent modification used for nanocellulose [29, 30]. 

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