title: Formation of polyelectrolyte multilayers from polysaccharides at low ionic strength.
abstract: Layer-by-layer deposition of sodium carboxymethylcellulose (NaCMC) and chitosan (CHI) was used to create polyelectrolyte multilayers on ellipsoidal beta-FeOOH particles at low ionic strength. Using electro-optics, we investigated the formation of films in dependence on the polyelectrolyte charge density by controlling pH of the dipping solutions. We found out a linear growth of the CMC/CHI films when they are constructed from highly charged CHI (at pH 4.0) and weakly charged NaCMC (at pH 4.0 and 5.5). The hydrodynamic thickness of the film constructed at pH 4.0/4.0 is unusually large for a linearly growing film (ca. 220 nm after deposition of 8 bilayers), but it strongly decreases (ca. 4 times) with increasing ionization of NaCMC (at pH 5.5). In both cases, the multilayer buildup proceeded through a series of adsorption-desorption steps. This was explained by a partial loss of CHI from the film surface on exposure to the solution of longer NaCMC molecules. The irregular film growth correlated quite well with the variations in the electrical polarizability of the polymer-coated particles. This correlation enabled us to conclude that the adsorption of both polymers occurs only on the film surface, with no diffusion in and out of the film bulk during deposition of each CMC/CHI bilayer.
authors.affiliation: Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria. radeva@ipc.bas.bg
authors.forename: Tsetska
authors.initials: T
authors.lastname: Radeva
authors.forename: Kamelia
authors.initials: K
authors.lastname: Kamburova
authors.forename: Ivana
authors.initials: I
authors.lastname: Petkanchin
mesh_terms: D000327:Adsorption; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D008567:Membranes, Artificial; D009994:Osmolar Concentration; D012964:Sodium / Q000737:chemistry; D013499:Surface Properties
chemical_list: D008567:Membranes, Artificial; D048271:Chitosan; D012964:Sodium; D007501:Iron; D002266:Carboxymethylcellulose Sodium