Chitosan reactivity

Ruiza, M Sastreb, AM Guibalc, E. Palladium Sorption on Glutaraldehyde-Crosslinked Chitosan. Reactive Functional Polymers, 2000, 45,155-173. 

Chitosan (> 75% deacelylation, 800-2000 cps) was mixed wilh stock so-lulions of Cu(II), Fe(ll), Cd(ll) and Zn(II), prepared in 0.1 M HNO3, and of Ca(ll) and Mn(II), in 0.1 MHCl. It was found that, in the chelation of most metal ions by chitosan, 1 1 binding of chitosan is more dominant than 2 1 cooperative binding, but vice versa for Zn(II) and Cd(II). The chelation of Cu(II) by chitosan showed much higher reactivity when compared to other divalent metal ions. Cu(II), Fe(II), Cd(II) andZn(II) showed strong reactivity and stability of their chelates. In contrast, the interactions between Ca(II) or Mn(II) and chitosan were almost negligible. These data confirm brilliantly previous data by Muzzarelli et al. [116]. 

The early works by Muzzarelh et al. [179] showed that tyrosinase converts a wide range of phenohc substrates into electrophihc o-quinones [180]. Tyrosinase was used to convert phenols into reactive o-quinones which then underwent chemical reactions leading to grafting onto chitosan. A review article showed that in general the tyrosinase-catalyzed chitosan modifications resulted in dramatic changes in functional properties [181]. 

The general chemical behavior of chitosan, however, should be considered in order to avoid certain difficulties stemming from its insolubility at pH higher than 6.5 and its reactivity under the thermal conditions of the sprayer. For example, spray-drying of 1-2% chitosan in acid solution at 168 °C seems... 

A novel fiber-reactive chitosan derivative was synthesized in two steps from a chitosan of low molecular weight and low degree of acetylation. First, a water-soluble chitosan derivative, N-[(2-hydroxy-3-trimethylammonium)-... 

Chitosan is the main structural component of crab and shrimp shells. Chitosan contains both reactive amino and hydroxyl groups, which can be used to chemically alter its properties under mild reaction conditions. Al-acyl chitosans were already reported as blood-compatible materials. UV irradiation grafting technique was utilized to introduce obutyrylchitosan (OBCS) onto the grafted SR film in the presence of the photosensitive heterobifunctional cross-linking agent. The platelet adhesion test revealed that films grafted on OBCS show excellent antiplatelet adhesion. 

Zhi, J., Wang, Y., Lu, Y., Ma, J. and Luo, G. (2006) In situ preparation of magnetic chitosan/Fe304 composite nanoparticles in tiny pools of water-in-oil microemulsion. Reactive and Functional Polymers, 66, 1552-1558. 

Chang, Y.C., Chang, S.W. and Chen, D.H. (2006) Magnetic chitosan nanoparticles studies on chitosan binding and adsorption of Co(II) ions. Reactive and Functional Polymers, 66, 335-341. 

We initially prepared the first chitosan-sialoside hybrid 19 by treating 80% de-AT-acetylated chitosan with p-formylphenyl a-sialoside 6 (Scheme 1) under reductive amination conditions (NaBH3CN) (Scheme 7) [64]. The level of sialo-side incorporation could be controlled by increasing the amount of 6 (Table 15.2). The reactivity of aldehyde 6 toward chitosan was found to be in the range 25-48% due to excessive reduction of the aldehyde under the acidic reaction conditions. Water-soluble materials were only achieved at high DS (DS > 0.53). Sialo-hybrids with lower substitutions were further derivatized with succinic... 

PAMAM-Chitosan 29a-e DS (NH2) Sialoside hybrid DS (Neu5Ac) Reactivity (%r... 

Chitosan films are also transparent in the UV and visible regions of the light spectrum and thus have little effect on most optical detection methods. Also, chitosan s amine groups are more reactive in aqueous environments compared to other polyamines because of the low pKa value possessed by the primary amine (6.3 for chitosan vs. 10.5 for polylysine). Finally, other advantages of chitosan are that it is safe, abundant and inexpensive. 

T0565 Northern Watertek Corporation, Atomizing Freeze Crystallization—Snowfluent T0572 Oak Ridge National Laboratory, Mercnry Removal by Reactive Leaching T0583 Oregon State University, Chitosan Beads... 

T0510 Metals Recovery, Inc., Metals Leaching T0583 Oregon State University, Chitosan Beads T0601 Permeable Reactive Barriers (PRBs)—General T0668 Rochem Environmental, Inc., Disc Tube... 

Aiba, S. (1989). Studies on chitosan 2. Solution stability and reactivity of partially N-acetylated chitosan derivatives in aqueous media. Int. ]. Biol. Macromol. 11, 249-252. 

Another way to achieve desirable polymer properties is the modification of preformed polymers. This modification may take place on the reactive sites of the polymer chain through alkylation, hydrolysis, sulfonation, esterification, and other various reactions of polymers. Examples of natural polymers and their modifications are cellulose and its derivatives, chitin and chitosan, and polysaccharides. These are still to this day very important polymers for pharmaceutical applications. 

---