Miniemulsions via in situ Surfactant Generation

Abstract

The preparation and stabilisation of miniemulsions using in situ generated surfactants is described. Neutralising a water‐soluble base with an oil‐soluble long‐chain acid instantaneously generates in situ surfactants at the oil/water interface, resulting in a rapid homogenisation/polymerisation process. It was found that droplet sizes decreased with surfactant concentration and solid content and that in situ generated potassium stearate is not capable of simultaneously serving as a surfactant and costabiliser. However, the presence of stearic acid delays the rate of ripening. A number of in situ surfactants were prepared with different acids and bases. It was found that the droplet size decreased with the hydrated radius of the counterions.magnified image

Miniemulsion polymerization based on in situ surfactant formation without high-energy homogenization: effects of organic acid and counter ion

“…Miniemulsion polymerization based on in situ surfactant formation Y Guo et al differ from our results; however, it must be kept in mind that El-Jaby et al 32 used high-energy homogenization as well as different monomers. These authors cited possible contributing factors as the influence of carboxylic acid chain length on the hydrophobicity of the monomer phase, as well as the extent of surfactant side reactions.…”

“…Of course, other factors may well be at play. El-Jaby et al 32 reported that in miniemulsion copolymerizations of methyl methacrylate and butyl acrylate employing the in situ surfactant technique (with KOH) in tandem with high-energy homogenization, the particle size (after polymerization) increased in the order LAoSAoBA. These results Table 1.…”

“…All the other combinations resulted in phase separation, coagulation or extremely viscous mixtures. El-Jaby et al 32 reported that for miniemulsion copolymerizations of methyl methacrylate and butyl acrylate employing the in situ surfactant technique (using SA) in tandem with high-energy homogenization, the initial droplet diameters increased in the order K + oNa + oLi + . In all cases, good emulsion stability was observed and the polymerizations proceeded according to a miniemulsion mechanism.…”

“…It has also been demonstrated that surfactant generation at the interface combined with high-energy miniemulsification results in more rapid generation of a given droplet size than with preformed surfactant. 31,32 Under unsuitable conditions (in terms of ratio of base to acid and amount of surfactant generated), the in situ surfactant technique results in systems that proceed mainly via an emulsion polymerization mechanism. 33 We have reported that the in situ surfactant technique can also be successfully applied to nitroxide-mediated radical polymerization.…”

Synthesis of Nanosized (<20 nm) Polymer Particles by Radical Polymerization in Miniemulsion Employing in situ Surfactant Formation

“…[41] High energy mechanical homogenization devices in tandem with the in situ surfactant technique results in more rapid production of a given droplet diameter than when using a preformed surfactant. [42,43] The present Communication describes a novel miniemulsion polymerization approach for synthesis of nanosized polymer particles by combination of the in situ surfactant generation technique and high-energy homogenization at relatively high surfactant content. This technique enables synthesis of polymeric nanoparticles with diameters as low as <20 nm in a one-step process (no monomer feed) using considerably less surfactant than a microemulsion system.…”