Enthalpic stabilisation

These effects have been observed for both aqueous and non-aqueous media and good correlation between the point of incipient flocculation and the 0-temperature is well established112. The transition from stability to instability usually occurs over a very narrow temperature range (1 or 2 K). Enthalpic stabilisation tends to be the more common in aqueous media and entropic stabilisation the more common in non-aqueous media. Owing to the elastic effect, aggregation into a deep primary minimum does not take place (as is possible with lyophobic sols) and redispersion takes place readily on reverting to better than 0-solvent conditions. 

Figure 7.7 Enthalpic stabilisation representation of en-thalp ic stabilisation of particles with adsorbed hydrophilic chains. The hydrated chains of the polyoxyethylene molecules —(0CH2CH2) 0H protrude into the aqueous dispersing medium. On close approach of the particles to within 26 (twice the length of the stabilising chains), hydrating water is released, resulting in a positive enthalpy change which is energetically unfavourable.

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