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

Abstract

A novel method for synthesis of ultrafine polymeric nanoparticles of diameters less than 20 nm has been developed. The method is based on miniemulsion polymerization exploiting combination of the in situ surfactant generation approach (whereby the surfactant is formed at the oil-water interface by reaction between an organic acid and a base) and ultrasonication. Conventional radical polymerization and nitroxide-mediated radical polymerization of styrene have been conducted in miniemulsion using oleic acid/potassium hydroxide, demonstrating that particles with diameters less than 20 nm can be obtained by this approach at surfactant contents much lower than traditionally required in microemulsion polymerizations.

Experimental investigation on thermal properties of silver nanofluids

“…The OA group helped with the homogeneous dispersion of the nanoparticles in the nanofluids. Moreover, the potassium cation (K + ) significantly contributed to accruing the thermal property increase, which had effects on the heat transfer rate mechanism more efficiently than the thermal diffusion in the fluid (Guo and Zetterlund, 2011;Hwang et al, 2008;Kwak and Kim, 2005;Wang et al, 2012).…”

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).…”

An investigation into the nature and potential of in-situ surfactants for low energy miniemulsification

“…In its current state, the large quantity of surfactant required for the KOH/oleic acid system will hinder the industrialization of this process for application in miniemulsion polymerization, and results in the same issues that beset many low energy miniemulsification techniques, including phase inversion and dilution of microemulsions, such as the need for high surfactant, low oil content systems. [23][24][25]32 Only through the discovery of an acid-base pair that is capable of formation of a high fraction of nanosized droplets at significantly lower surfactant concentration than the KOH/oleic acid system would the in-situ technique be a viable alternative to the formation of miniemulsions using traditional surfactants and high shear devices.…”

“…Many seemingly contradictory articles have since been published that have argued that droplet nucleation can dominate and it is possible to obtain stable miniemulsions with only gentle agitation under certain conditions. Thus, Guo et al 30,32 have shown that, for low solid content and at higher surfactant concentrations than used by Saygi-Arslan et al 27 , the in-situ technique can be used to prepare stable miniemulsions and, by use of experiments with aqueous phase radical scavengers and investigations into the extent of droplet nucleation, that the polymerization proceeds via the miniemulsion reaction mechanism. Similarly, El-Jaby et al, 28,29 working at much higher solids content (40 wt%), have shown that, using a rotor-stator, the in-situ technique allowed reaching the smallest droplet size of the miniemulsion faster than using either the preformed surfactant or a classical surfactant (sodium dodecylbenzenesulfonate (SDBS)).…”