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

Abstract

Miniemulsion polymerization of styrene based on the in situ surfactant-generation technique has been investigated for a range of carboxylic acids and counterions. This technique relies on in situ formation of the surfactant at the oil-water interface and circumvents the use of traditional high-energy mixing (for example, ultrasonication) for generation of the initial miniemulsion. Miniemulsion polymerizations have been conducted successfully using the carboxylic acids lauric acid, palmitic acid and oleic acid, respectively. Coagulation/phase separation was not observed and the number-average particle diameters were o100 nm. The counterions K + , Na + and Li + were investigated in combination with five different carboxylic acids (all permutations), revealing that satisfactory miniemulsion formation/stability could only be obtained with K + . Results of miniemulsion polymerizations conducted in the presence of an aqueous-phase radical scavenger were consistent with predominant monomer droplet nucleation. Use of the corresponding preformed surfactants added to the aqueous phase, without high-energy mixing, did not result in sufficiently stable initial (before polymerization) miniemulsions.

Radical polymerization of miniemulsions induced by compressed gases

“…Another low energy approach is based on in situ formation of surfactant at the oil/water interface. 17,[28][29][30][31][32][33][34][35] An organic acid dissolved in the organic phase undergoes reaction at the interface with a base located in the aqueous phase, generating the surfactant at the interface. Although great progress has been made, some of these methods are not easily implemented (EIP method) or incompatible with thermally initiated radical polymerization (PIT method).…”

Styrene-Butadiene Rubber by Miniemulsion Polymerization Using In Situ Generated Surfactant

“…This behavior is valuable from a commercial point of view as it suggests that the miniemulsions can be prepared and stored for several days before use. Several studies have described the formation of miniemulsions using in situ generation surfactant [ 21 , 22 , 23 ]. In all cases, the authors state that they obtained stable miniemulsions, but did not investigate the long-term stability of the products.…”

Dynamic Imine Chemistry at Complex Double Emulsion Interfaces

“…[29][30][31][32] Additionally, imine bond equilibria are pH sensitive, allowing for manipulation of the bond and therefore the structures of double emulsions (Figure 1b). Although there are reported examples of in situ molecular surfactant generation for single emulsions, including deprotonation of carboxylic acids and metallosurfactants, [33][34][35][36][37][38][39] and Pickering single and double emulsions, [30][31] we are unaware of any prior reports of double emulsion fabricated via in situ molecular surfactant synthesis.…”