Interactions between cellulose and colloidal silica in the presence of polyelectrolytes

The forces acting between two cellulose surfaces and a cellulose surface and silica have been investigated using the interferometric surface force technique and the scanning force microscopy colloidal-probe technique. A key element in this study is the preparation of very smooth cellulose surfaces using the Langmuir-Blodgett technique, which facilitates a detailed characterization of the forces acting between the surfaces as a function of their separation. The main part of the investigation is concerned with the effect of a highly charged cationic polyelectrolyte, poly[[2-(propionyloxy)ethyl]trimethylammonium chloride] (PCMA), on the interaction between negatively charged silica and uncharged cellulose. It is found that the presence of the cationic polyelectrolyte reduces the force barrier against flocculation, but also the attractive pull-off force. The implications of these findings for the function of this polyelectrolyte as a retention aid and a wet strength additive is discussed. The ionic strength of the solution has profound effects 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.