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ZWITTERIONIC CELLULOSES: CHEMICAL FUNTIONALIZATION, CHARACTERIZATION AND POSSIBLE APPLICATIONS
One of the most abundant natural polymers is cellulose composed of linear chains of anhydroglucose repeat units linked together through the β 1→4 glycosidic bonds. As polysaccharide, their principal active functional groups are OH´s. Those moieties can be chemically modified by means of addition, substitution and oxidation reactions conferring new properties to cellulose. Chemical functionalization concerning to introduce ionic character to cellulose such as cationic and anionic moieties have been an important topic of study. However, only few approaches have explored the modification with zwitterionic groups in cellulose and their potential use in several applications. Recently investigations in our group showed that introducing amino acids on cellulose fibers contribute to increase the interfiber bonding strength in paper sheets. Solid state 13C and 15N NMR analyses have been employed for the characterization of the zwitterionic cellulose and for determining the zwitterion form in this modified cellulose as well as their amino acid interactions on cellulose through the measurement of internuclear distances 13C-15N by REDOR experiment. On other hand, the potential of the zwitterionic interaction in cellulose can be also extended to different uses: 1) adsorption and separation systems for ions (textile dyes uptake in polluted water); 2) new adhesives and 3) biotechnology applications such as enzymes and cells immobilization for biocatalysis (recoverable catalytic systems). Some of these applications are now investigated in collaboration with the Biotechnology group of our department as well as different reactions pathways for obtaining the most appropriated zwitterionic celluloses for these purposes. Since the synthesized zwitterionic materials are solids and will be applied in this form, the chemical modification of cellulose is evaluated by FTIR and solid-state NMR techniques. In general, the present work shows the possibility of synthesizing zwitterionic cellulose, their spectroscopic characterization as well as the great potential of application in some fields.