A study on the interaction of cationized chitosan with cellulose surfaces

This investigation describes the interaction of trimethyl chitosans (TMCs) with surfaces of cellulose thin films. The irreversible deposition/adsorption of TMCs with different degrees of cationization was studied with regards to the salt concentration and pH. As substrates, cellulose thin films were prepared by spin coating from trimethylsilyl cellulose and subsequent regeneration to pure cellulose. The pH-dependent zeta potential of cellulose thin films and the charge of TMCs were determined by streaming potential and potentiometric charge titration methods. A quartz crystal microbalance with dissipation monitoring was further used as a nanogram sensitive balance to detect the amount of deposited TMCs and the swelling of the bound layers. The morphology of the coatings was additionally characterized by atomic force microscopy and related to the adsorption results. A lower degree of cationization leads to higher amounts of deposited TMCs at all salt concentrations. Higher amounts of salt increase the deposition of TMCs. Protonation of primary amino groups results in the immobilization of less material at lower pH values. The results from this work can further be extended to the modification of regenerated cellulosic materials to obtain surfaces, with amino- and trimethylammonium moieties.