Criteria for effective steric stabilisation

1) The partides should be completely covered by the surfactant or polymer (the amount of surfactant or polymer should correspond to the plateau value). Any bare patches may cause flocculation, either by van der Waals attraction (between the bare patches) or by bridging flocculation (whereby a polymer molecule will become simultaneously adsorbed onto two or more partides). 

2) The chain should be strongly anchored to the partide surfaces, to prevent any displacement during partide approach this is particularly important for concentrated suspensions. For this purpose, A-B, A-B-A block and BA graft copolymers are the most suitable, where the chain B is chosen to be highly insoluble in the medium and has a strong affinity to the surface. Examples of B groups for hydrophobic particles in aqueous media are polystyrene and poly(methylmethacrylate). 

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Several criteria can be estabhshed for effective steric stabilisation ... 

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