INTERACTIONS BETWEEN CELLULOSE AND COLLOIDAL SILICA IN THE PRESENCE OF POLYELECTROLYTES

The forces acting between two cellulose surfaces and a cellulose surfa ce and silica have been investigated using the interferometric surface force technique and the scanning force microscopy colloidal-probe tec hnique. A key element in this study is the preparation of very smooth cellulose surfaces using the Langmuir-Blodgett technique, which facili tates a detailed characterization of the forces acting between the sur faces as a function of their separation. The main part of the investig ation is concerned with the effect of a highly charged cationic polyel ectrolyte, poly[[2-(propionyloxy)ethyl]trimethylammonium chloride] (PC MA), on the interaction between negatively charged silica and uncharge d cellulose. It is found that the presence of the cationic polyelectro lyte reduces the force barrier against flocculation, but also the attr active pull-off force. The implications of these findings for the func tion of this polyelectrolyte as a retention aid and a wet strength add itive is discussed. The ionic strength of the solution has profound ef fects on the interactions between cellulose and silica in the presence of PCMA. This is due to a decreased polyelectrolyte-surface affinity at higher ionic strengths. (C) 1997 Elsevier Science B.V.