Carboxyl Cellulosic

Esterification with poly(carboxylic anhydride)s can be controlled to minimize diesterification and cross-linking to produce carboxylated cellulosic... 

Montanari, S., Rountani, M., Heux, L., and Vignon, M. R., Topochemistry of carboxylated cellulose nanocrystals resulting from TEMPO-mediated oxidation. Macromolecules 2005, 38 (5), 1665-1671. 

Cellulose, acetates, propanoates, reaction prods, with ozone. See Cellulose acetate propionate carboxylate Cellulose acetate trimellitate CAS 52907-01-4... 

Esterification with poly(carboxylic anhydrides) can be controlled to minimize diesterification and crosslinking to produce carboxylated cellulosic esters. Eastman Kodak in a recent patent claimed the succinylation of cellulose to different degrees 1 per 3 anhydroglucose rings [182] and 1 per 2 rings [183]. Henkel [184] also has a patent for a surfactant by the esterification of cellulose with alkenylsuccinic anhydride, presumably substitution degree governs the hydrophile-hydrophobe balance of the product and its surfactant properties. 

Samples (2mg), i.e. 4-amino TEMPO, polyglucuronic acid-4-amino TEMPO and surfaced carboxylated cellulose nanocrystals-4-amino TEMPO, were dissolved in H2O (ImL) and loaded into a closed capillary tube (o.d. 0.7 mm) which was introduced in a standard EPR... 

For partially oxidation leading to surface carboxylated cellulose nanocrystals, the TEMPO mediated oxidation led to approximately constant molar yields of oxidized nanocrystals more or less constant, 92-95% with cotton linters (and for soluble fractions 4-7%) (Figure 16). The global yields for hydrolyzed samples were always 100%. Montanari [95] indicated that the cellulose samples which are not hydrolyzed before oxidation presented lower global yields with increasing NaOCl concentrations. The values decreased to around... 

From these observations, the TEMPO mediated oxidation of cellulose nanocrystals is performed with 1 mol NaOCl / 1 mol glycosyl unit (1 eq). The carboxyl groups content of surface carboxylated cellulose nanocrystals was determined by conductometric titrations with very reproducible results and the value is 0.15 for cotton linters (Figure 16). 

The solid-state NMR characteristics of surface carboxylated cellulose nanocrystals and liquid-state chemical shift data of polyglucuronic acid are given in Table 6 with the main appearance of the peak near 175 ppm and the FTIR peak at 1730 cm corresponding to carboxyl moiety. The FTIR characterization of these oxidized cellulose samples is shown in Table 7. 

Table 6. The C NMR characteristics of polyglucuronic acid (liquid-state) and surface carboxylated cellulose nanocrystals (solid-state).

Grafting reaction onto surface carboxylated cellulose nanocrystals... 

From native cellulose, a partial conversion into surface carboxylated cellulose nanocrystals has been realized owing to its high aystaUinity and its poor accessibility of primary hydroxyl groups engaged in both intra and inter molecular hydrogen bonds in the native cellulose structure. The oxidation led to a two-phase solution water-soluble and water-insoluble fractions. These two fractions corresponded to the totally oxidized polyglucuronic acid and the surface carboxylated cellulose nanociystals, respectively. 

The grafting reaction by carbodiimide mediated amidation process is carried out onto surface carboxylated cellulose nanoaystals with nitroxide radical (4-amino TEMPO). A suspension is obtained. Thereafter, the purification of products included precipitation, dialysis and freeze-diying steps. The reaction yields were of 98% with cotton linters. This slight loss of materials can been explained by partial degradation of grafting product. The importance of material loss depended on the crystal size of cellulose whiskers which is more important when the soluble fraction is high. The products issued to grafting reaction were analyzed by conductimetry, elemental analysis. FTIR, NMR and EPR spectroscopies. 

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