Poly emulsion particle formation

An example for a nanoparticle system undergoing a phase transition of the matrix is given by nanospheres and nanocapsules from poly-e-caprolactone (PCL) formed by the emulsion-diffusion technique. In this case, the mechanism of particle formation in an o/w emulsion is based on the diffusion of an organic solvent into the continuous phase followed by the deposition of the polymer around an oil droplet (Fig. 20). 

Foil laminations usually call for resins, but even here a small amount of starch is often added for its smoothing properties. One example is poly(vinylalcohol) 3, starch 3, water 49, potassium persulfate 0.1 add dropwise a mixture of 5 dibutyl phthalate and 39 vinyl ace-tate at 70°C (158°F), dilute to 25% solids. Starch at 3-15% is claimed to prevent coarse particle formation in the following formulation 45 % aqueous emulsion containing 1 99 acrylic acid vinyl acetate copolymer 100, com starch 4, poly(vinylalcohol) 5, dibutyl phthalate 15. Aluminum foil was coated on paper at 300 m / min (meters per minute) without coarse particle formation, while a similar formulation omitting the starch formed coarse particles at 90 m/min. ... 

Silica particles synthesized in nonionic w/o microemulsions (e.g., poly-oxythylene alkyl phenyl ether/alkane/water) typically have a narrow size distribution with the average value between 25 and 75 nm [54,55]. Both water and surfactant are necessary components for the formation of stable silica suspensions in microemulsions. The amounts of each phase present in the micro emulsion system has an influence on the resulting size of the silica nanoparticle. The role of residual water (that is the water that is present in the interface between the silica particle and the surfactant) is considered important in providing stability to the silica nanoparticle in the oil... 

When water-soluble initiators and surface-active agents are used, relatively stable latices are formed from which the polymer cannot be separated by filtration. In the case of vinyl acetate, the distinctions are more blurred. Our description of Procedure 3-3 above represents a transitional situation between a solution and a suspension process since the product separated from the reaction medium. Between the true suspension and the true emulsion polymerization, we find, according to Bartl [4], the processes for formation of reasonably stable dispersion of fine particles of poly(vinyl acetate) using reagents which are normally associated with suspension polymerization. The product is described as creme-like. The well-known white, poly(vinyl acetate), household adhesives may very well be examples of these creamy dispersions. The true latices are characterized by low viscosities and particles of 0.005-1 /im diameter. The creme-like dispersions exhibit higher viscosities and particle diameters of 0.5-15 fim. 

Highly purified diallyl maleate and fumarate in an inert atmosphere, are said to polymerize very rapidly [118], However, trace impurities and atmospheric oxygen substantially reduce the polymerization rate under ordinary circumstances. Naturally with the double bond between the two carboxylate groups and the two allylic double bonds, crosslinking takes place at very low conversion. Even so, in copolymer systems such as in poly(vinyl acetate) emulsion copolymers, the cross-linking of a fumarate or maleate within the latex particles appears not to interfere significantly with film formation properties. As a matter of fact these monomers are incorporated in poly(vinyl acetate) latices used in adhesives and in water-based paints. 

Modified poly(methacrylic acid) microparticles complexed with gadolinium(lll) (Gd ) ions were prepared at 100 nm by Michinobu [81]. The emulsion tcrpolymerization of methacryhc acid, ethyl acrylate, and aUyl methacrylate and the following complexation with Gd ions yielded the polymer particles with different Gd ion contents. Potentiometric titration of the complexation of the particle with Gd + ions indicated the formation of a very stable tris-carboxylate coordinate complex with the Gd + ion. The microparticles dispersed on a mica substrate were subjected to AFM, followed by MFM. AFM showed 100-nm-sized and monodispersed spherical images. The following MFM... 

---