Interaction forces between toner surfaces

The interaction of toner particles in aqueous solution is of interest with regard to both fundamental and practical aspects of de-inking processes. It has been established for the toner studied that the toner polymeric resin, that is, the block copolymer styrene-methyl methacrylate, more specifically the polymethyl methacrylate, has a tremendous influence on the interaction between toner particle surfaces. Interaction force profiles for toners are dependent oil the pH conditions, going from attraction to repulsion as the alkalinity of the aqueous medium increases. Both the attraction and repulsion behavior is largely a result of the conformation of polymethyl methacrylate (PMMA) segments. Under strongly acidic conditions the PMMA segments are coiled and toner particles are attracted to each other due to hydrophobic interaction while for alkaline conditions the PMMA segments are more extended into the solution and the toner particles remain dispersed due to steric forces.