Phase behaviour of a non-ionic surfactant–polymeric solution–water system during the phase inversion process

Abstract

A phase inversion method for making colloidal polymer composites is being considered. That method requires the formation of fine and stable emulsions of polymerisable monomer containing another kind of polymer. Suitable emulsions might be produced via phase inversion. Therefore, the phase behaviour of dispersions containing non-ionic surfactant, non-aqueous polymer solutions (polyisobutene in styrene) and was investigated. Phase inversion maps, showing the behaviour of the emulsion system as a function of hydrophilic–lipophilic balance (HLB) and water volume fraction, are developed. Two types of non-ionic surfactants, polyoxyethylene sorbitanmonolaurate (SML), or polyoxyethylene nonylphenyl ether (NPE), were used in the study. There are two types of phase inversion (catastrophic and transitional) and, in some circumstances, complex drops may be formed. Five phase inversion boundaries have been found in the NPE system. These include one transitional inversion boundary and four catastrophic inversion boundaries. Unlike the NPE system, there are two transitional phase inversion boundaries in the SML system. With the non-aqueous solutions used here, a stable polymer emulsion with sub-micron polymer drops could not be produced by using the transitional inversion route with either surfactant. However, it was possible to produce a stable polymer emulsion with sub-micron drops by approaching the catastrophic inversion condition. A drop size of about 500 nm was obtained by using a mixture of SML surfactants. As the “unstable” catastrophic inversion region is approached closely, the complex drops increased in size and became less stable.