Polyelectrolyte adsorption onto cellulose fibres - A review

This review focuses upon the following questions: a) Why are the polyelectrolytes adsorbed onto cellulosic fibres? The easiest way to describe the adsorption is as an interaction between the charges on the fibres and the charges on the polyelectrolytes. However the entropy gain upon the release of counterions to the charges on the fibres and the polyelectrolytes gives a much larger contribution to the adsorption energy than the charge interaction. There are some investigations which clarify the influence of certain basic parameters on the fibres and the surfaces and these investigations will be reviewed. An attempt will also be made to create a link between published adsorption data and the Scheutjens-Fleer theory for polyelectrolyte adsorption. Another important question is how the polyelectrolytes are adsorbed on the fibres, i.e. are the segments only found in trains on the surface or will there be some loops and/or tails protruding into the solution? Very little is known about this but the topic will be discussed in some detail. b) Where are the polyelectrolytes adsorbed - on the external surfaces of the fibres or within the fibre wall and how is this related to the molecular properties of the polyelectrolytes? There are a lot of definitions in the literature about fibre surfaces, external surfaces etc. but it is important to link the adsorption to molecular properties and the work in this area will be reviewed. The influence of fines will also be discussed. c) What controls the kinetics of polyelectrolyte adsorption and are there models to describe this adsorption? It is still not entirely known how polymers that adsorb onto the internal surfaces of the fibres are then transported through the fibre wall. The work conducted in this area will be reviewed, It is also important to know the kinetics of the reconformation of the polymer on the fibre surface and this topic will also be discussed in detail. Finally the kinetics of desorption will be treated.