Surfactants as stabilizers

The properties of a latex depend on the nature of polymers in the latex, particularly the monomer ratio in copolymers and the type and amount of plasticizers. The monomer ratio affects the strengths of the latex modified mortars to the same extent as the polymer-cement ratio [87, 92]. Mechanical and chemical stability, bubbling and coalescence on drying all depend on the type and amount of surfactants and antifoamers and the size of dispersed polymer particles. It is important that the use of selected antifoamers and surfactants as stabilizers or emulsifiers produces no adverse effect on cement hydration. 

Piirma I. Polymeric surfactants as stabilizers in aqueous emulsion polymerization. In Polymeric Surfactants, Surfactant Science Series. Vol. 42, New York Marcel Dekker, 1992 127-164. 

Chun, H., Amphoteric surfactants as stabilizers for cosmetic type emulsions, in Proceedings of the 1978 Annual Scientific Seminar of the Society of Cosmetic Chemists, 1, December 1978. 

A parallel study has reported the synthesis of crosslinked polymer microspheres in supercritical carbon dioxide [54]. Heterogeneous free-radical polymerization of divinyl benzene and ethyl benzene were carried out at 65 C and 310 bar using AIBN initiator to form the crosslinked polymer. It is shown that in the absence of surfactants as stabilizers, polymerization of the mixture containing 80 % divinyl benzene + 20 % ethyl benzene leads to poly(divinylbenzene) microspheres of about 2.4 micron diameter [Figure 14]. In the presence of a carbon dioxide-soluble diblock copolymer as a stabilizer, polymerization of the mixture with the same monomer ratio proceeds as an emulsion and lead to smaller crosslinked particles (ca. 0.3 micron). Thermal analysis shows that the crosslinked polymer that is formed from these polymerizations is stable up to 400 C. 

Paclitaxel ASD ASD of paclitaxel was prepared with SAS using series of polymers and surfactant as stabilizers (Woo et al. 2006). The drug, polymer, and stabilizer were dissolved in an organic solvent such as ethanol and dichloromethane. This solution was then sprayed into a vessel containing SCF, to produce a highly uniform, nanoscale ASD. The solubility of the paclitaxel solid dispersion prepared by the SAS process was significantly higher than the untreated paclitaxel. 

Stable dispersion of cellulose microcrystals in nonpolar solvents by using surfactants as stabilizing agents [157]... 

Adsorbed surfactant layers present a different problem for theoretical analysis, especially if there is multilayer adsorption. Configurational entropy would not seem to be high in monolayers of molecules such as C12E6 which are vertically adsorbed and close-packed at the interface. Further problems arise when considering additives in the bulk phase which are incompatible with the stabilizing molecules under some conditions. As far as we are aware no one has considered this problem with surfactants as stabilizers. However, the effect of free polymer on the stability of sterically stabilized dispersions in which a polymer is used as stabilizer has been considered [41]. When two dilute polymers in the same solvent are mixed, they are, as a rule incompatible and will exhibit phase separation. Addition of free polymer (type i) to a polymer (type ii)-stabilized dispersion is likely to lead to instability [42]. However, it has been found, for... 

FIG. 2 Ultraviolet absorbance of silver colloids prepared in the presence of various surfactants as stabilizers. 

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