Sajjadi Shahriar
Division of Engineering, ECLAT, King's College London, London, UK.
Langmuir. 2006 Jun 20;22(13):5597-603. doi: 10.1021/la060043e.
Emulsification processes are usually characterized by the way they allow the surfactants, as well as the dispersed phase, to be incorporated into emulsions. A model cyclohexane-in-water emulsion using a pair of polyoxyethylene nonylphenyl ether surfactants, one oil-soluble and one water-soluble, was considered. Two surfactant mixing approaches consisting of mixed surfactants (agent-in-oil and agent-in-water) and segregated surfactants (agent in corresponding oil and water phases) were used to produce the model emulsion. Formation of oil-in-water nanodroplets could be only achieved if emulsification was associated with the formation of a three-phase microemulsion structure (transitional phase inversion) across the path. This occurred only if segregated surfactants were used in a process in which water was added to oil. With decreasing surfactant concentration, a point was reached below which the inversion mechanism transformed from transitional to catastrophic, leading to the formation of large droplets. The transformation was also accompanied by a shift in the evolution of the drop size. Drop size variations showed a minimum at the inversion point for the transitional phase inversion, whereas they showed a maximum for the catastrophic phase inversion. The agent-in-oil technique followed a catastrophic phase inversion mechanism and ranked second in terms of drop size.
乳化过程通常以其使表面活性剂以及分散相融入乳液的方式为特征。考虑了一种使用一对聚氧乙烯壬基苯基醚表面活性剂（一种油溶性和一种水溶性）的水包环己烷模型乳液。采用两种表面活性剂混合方法，即混合表面活性剂（油包剂和水包剂）和分离表面活性剂（相应油相和水相中的剂）来制备模型乳液。只有当乳化与在整个过程中形成三相微乳液结构（过渡相转变）相关联时，才能实现水包油纳米液滴的形成。这仅在将水加入油中的过程中使用分离表面活性剂时才会发生。随着表面活性剂浓度的降低，会达到一个点，低于该点时，转变机制从过渡型转变为灾难性转变，导致形成大液滴。这种转变还伴随着液滴尺寸演变的变化。对于过渡相转变，液滴尺寸变化在转变点处显示最小值，而对于灾难性相转变则显示最大值。油包剂技术遵循灾难性相转变机制，在液滴尺寸方面排名第二。
