Polymer-stabilized emulsions

Huber Ch., Werner T., Krause Ch., Wolfbeis O.S., Novel Chloride-Selective Optode Based on Polymer-Stabilized Emulsions Doped with a Lipophilic Fluorescent Polarity-Sensitive Dye. Analyst 1999 124 1617. 

Recently, nonionic ortho ester surfactants have been used as emulsifiers for squalene, a polar oil [65]. In this case a polymer is used together with the surfactant. The emulsification is made under acidic conditions, and the surfactant breaks down rapidly after the emulsion is formed, leaving a surfactant-free, polymer stabilized emulsion with reasonable stability. 

Polymer-Stabilized Emulsions Influence of Emulsion Components on Rheological Properties and Droplet Size... 

To overcome temperature dependence of classic emulsions and to improve reproducible droplet sizes and skin compatibility, polymeric emulsifiers like dimethicones tpoly(siloxanes)] [12], poly(acrylamidosulfonic) acids (AMP) [13] and hydrophobically modified poly(acrylates) with Ci2-side chains [14] were used over the last years to substitute common surfactants. These polymer stabilized emulsions show good stability, high skin compatibility, even with sensitive skin types, high oil compatibility and a simplified production procedure [15]. 

The literature mentioned above on polymer-stabilized emulsions has, to our knowledge, dealt with emulsions containing only polymeric thickener or combinations of polymeric thickener and low molecular surfactants [21-29]. As a next step it seems rational to investigate systematically emulsions that combine the properties of polymeric thickener (acrylate) and polymeric emulsifier PEG-12. Knowledge on rheological properties of this type of emulsion might improve cosmetic applications, especially for sensitive skin types. Furthermore, it has to be clarified if there is a correlation between droplet size and elasticity in this type of emulsion. 

Epple M —) Maas M Felddtd Z Pettersson T Fischer K —> Diehl C Fluegel S Diehl C Gutberlet T Kolasihska M Hloucha M Kettler E Hoffmann H Song A Kappl M Zhang L Ketder E, Muller CB, Klemp R, Hloucha M, DOring T, von Rybinski W, Richtering W Polymer-Stabilized Emulsions Influence of Emulsion Components... 

Polymers have so far been used comparatively less than the common surfactants to stabilize emulsions in spite of the fact that excellent stabilization by them can be achieved (18—20). AppHcation probably has been limited because the adsorption of polymers to emulsion droplets has displayed some intricate phenomena small changes in polymer stmcture or in solvent properties may lead to drastic changes in adsorption. 

Cresylic acid is mainly used as degreasing agent and as a disinfectant of a stabilized emulsion in a soap solution. Cresols are used as flotation agents and as wire enamel solvents. Tricresyl phosphates are produced from a mixture of cresols and phosphorous oxychloride. The esters are plasticizers for vinyl chloride polymers. They are also gasoline additives for reducing carbon deposits in the combustion chamber. 

However, it appears that the pre-exponential factor Pq of the polymer-stabilized double emulsion is two decades smaller, resulting in a slower rate of leakage (see Figs. 6.18 and 6.19). Therefore, polymers are more suitable surface-active species to ensure long-term encapsulation in double emulsions than are short surfactant systems. 

Dickinson, E. (1997). Flocculation and competitive adsorption in a mixed polymer system relevance to casein-stabilized emulsions. Journal of the Chemical Society, Faraday Transactions, 93, 2297-2301. 

Formulas for emulsion polymerization also include buffers, free radical initiators, such as potassium persulfate (KiSiOs), chain transfer agents, such as dodecyl mercaptan (G sSTT). The system is agitated continuously at temperatures below 100°C until polymerization is essentially complete or is terminated by the addition of compounds such as dimethyl dithiocarbamate to prevent the formation of undesirable products such as cross-linked polymers. Stabilizers such as phenyl Beta-naphthylamine are added to latices of elastomers. 

It has also been observed consistently that frozen and thawed samples of non-F/T stable emulsions prepared with Triton X-405 and SLS exhibit significantly different characteristics. In the frozen and thawed samples of SLS-stabilized emulsions, the psuedo-crystalline coagulate separates cleanly leaving a relatively clear supernatant liquid. In the Triton X-405 samples, a white, swollen amorphous coagulate is obtained with an opaque supernatant liquid. These combined observations lend credence to the conclusion that Triton X-405 molecules are bound chemically to the polymer particles. 

Batch miniemulsion polymerization of MMA using PMMA as the costabilizer was carried out with SLS as the surfactant and KPS as the initiator. Solids content was kept at -30%. A low surfactant level was used with the miniemulsions to ensure droplet nucleation. The initiator concentration of the polymer-stabilized miniemulsion polymerizations was varied from 0.0005 to 0.02 Mjq, based on the total water content. An aqueous phase retarder, (sodium nitrite) or an oil-phase inhibitor (diphenylpicrylhydrazol [DPPH]), was added to both the miniemulsions and the macro emulsions prior to initiation. Particle numbers and rates of polymerization for both systems were determined. 

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