The interactions of amphiphilic latexes with surfaces: the effect of surface modifications and ionic strength

The effect of surface modifications brought about by a polymeric stabilizer on the interactions between polymer colloid particles and various substrates in aqueous media are directly measured using atomic force microscopy. The interactions of polystyrene particles with grafted hydrophilic ‘hairs’ of hydroxypropyl cellulose (denoted HPC/PS), of molecular weight ∼105, with mica, silica and graphite substrates are measured. HPC/PS is found to be compatibilized so that it will interact with both hydrophobic and hydrophilic substrates. The observed jump-to contact between HPC/PS and silica is characteristic of polymer solutions and is the result of the grafted hairy layer. Further direct evidence of HPC–substrate interaction is seen in a secondary adhesion with mica. The adhesion of the particles was found to follow the order silica>graphite>mica. The magnitudes of these interactions are rationalized in terms of the interactions of each of the substrate, core polymer and surface modification. It is concluded that the combined effects of surface roughness and hairy layer collapse due to compression give rise to the observed trend.