Nucleation Kinetics in the Krafft Transition(Poster session 2, New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)

Abstract

C16ピリジニウム界面活性剤のKrafft転移の動的過程が、過飽和溶液から結晶核が形成する過程と類似現象であること、結晶核形成誘導期間tが、過飽和度Sの対数の-3乗に比例すること、形成される水和固体が準安定の場合と安定状態の場合では、tとSの上記関係の比例係数が異なることを見出した。

The surfactant molecules with alkyl chains in the solid state at a decreased temperature form the hydrated crystal in water, which is called as the Krafft transition. The hydrated solids or crystals usually form the multilamella structures consisting of bilayers. Recently we have found the long-lived metastable hydrated solid in the Krafft transition process of cetylpyridinium chloride (CPC) in water through the measurements of the small-angle X-ray scattering, the electric conductance and the calorimetry. The multilamella structures in the metastable and stable solids, respectively, are composed of ordinary bilayers and interdigitated bilayers, which have been identified by their lattice spacings. It has been found that a time lag between drops of an electric conductance, k and a temperature, T exists in the Krafft transition process of CPC. The time lag is the induction period of the formation of hydrated solid, during which the molecules overcome the activation barrier in order to form a critical nucleation cluster.