Surface forces in aqueous polyvinylamine solutions. 2. Interactions between glass and cellulose

The forces acting between one surface coated with Langmuir-Blodgett cellulo se films and one glass surface have been measured using the MASIF surface f orce technique. This study is mainly concerned with the effects due to addi tion of cationic polyvinylamine and changes in ionic strength. The results have implications for the interactions between cellulose and mineral surfac es in the papermaking process. The cellulose surface is weakly negatively c harged at pH 5.5-6.0. Polyvinylamine adsorbs to both glass and cellulose su rfaces, which first causes charge neutralization and subsequently a charge reversal upon increasing the polymer concentration. The cellulose films swe ll upon immersion in aqueous solutions as evidenced by the appearance of a short-range steric force barrier. The dynamics of the swelling process was found to be dependent on the ionic strength of the solution. It was found t hat an increased ionic strength accelerates the swelling, which can be attr ibuted to an increase in surface charge density and hence an increase in th e short-range repulsion between individual cellulose chains. The results ob tained in this study are consistent with those obtained for the interaction between two glass surfaces in polyvinilamine solutions as described in a p revious report. However, the long-range (bridging) attraction observed betw een two glass surfaces immersed in the polyvinylamine solution was absent b etween one glass and one cellulose surface. We attribute this to the lower surface charge density of the cellulose surface.