Effects of surfactants on transition kinetics of stearic acid polymorphs

The effects of some nonionic surfactants on the kinetics of the solution-mediated transition of stearic acid of B and C polymorphs were studied. Some surfactants were found to retard the transition of the thermodynamically unstable stearic acid modification to the stable form in methanol, n-hexane and decane solutions. The surfactants consisting of large hydrophilic moieties revealed a significant retardation effect. The effect also depends on the solvent; the lower the solubility of the surfactant in the solvents, the more the transition rate was decreased. Finally it should be noted that the C→B transition was more affected than the B→C transition with a given surfactant.