Role of Surfactants in Condensation Methods

According to Gibbs [4] and Volmer [5], the free energy of formation of a spherical nudeus, AG, is given by the sum of two contributions a positive surface energy term AGg which increases with increase in the radius of the nucleus (r) and a negative contribution AGy due to the appearance of a new phase, which also increases with increasing r. 

AGs is given by the product of area of the nudeus and the specific surface energy (solid/liquid interfadal tension) y AGv is related to the relative supersaturation 

Equations (7.1) to (7.4) clearly show that the free energy of formation of a nucleus and the critical radius r above which the cluster formation grows spontaneously depend on two main parameters, y and (S/So) both of which are influenced by surfactants y is influenced directly, by adsorption of surfactant on the surface of the nucleus, which lowers y and this reduces r and AG. In other words, spontaneous formation of clusters occurs at smaller critical radii. In addition, surfactant adsorption stabilises the nuclei against any flocculation. The presence of micelles in solution also affects the process of nucleation and growth, both directly and in- 

According to the theory of Smith and Ewart [9] for the kinetics of emulsion polymerisation, the rate of propagation J p is related to the number of particles N formed in a reaction by the equation. 

According to Eq. (7.5), the rate of polymerisation and the number of particles are directly related, i.e. an increase in the number of particles will increase the rate. This has been found for many polymerisations, although there are excep- 

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