Graft copolymers particle size distribution

Styrene as matrix and polybutadiene as dispersed phase. During this phase inversion the above-mentioned graft copolymers act as polymeric emulsifiers and determine, inter alia, the particle size and particle size distribution of the dispersed polybutadiene phase. This morphology is fixed through another chemical reaction, that is the crosslinking of the polybutadiene phase. Therefore, the reaction mixture at the end of the prepolymerization period (at 30% conversion) does scarcely alter its morphology when it is polymerized to complete conversion, which is done without stirring mostly in bulk in a separate vessel. 

Particle size Distribution of Dispersion from Grafted Copolymers Made With Different Levels of Free Radical Initiator Concentration... 

Monomer compositional drifts may also occur due to preferential solution of the styrene in the mbber phase or solution of the acrylonitrile in the aqueous phase (72). In emulsion systems, mbber particle size may also influence graft stmcture so that the number of graft chains per unit of mbber particle surface area tends to remain constant (73). Factors affecting the distribution (eg, core-sheU vs "wart-like" morphologies) of the grafted copolymer on the mbber particle surface have been studied in emulsion systems (74). Effects due to preferential solvation of the initiator by the polybutadiene have been described (75,76). 

Here we discuss dispersion polymerizations that are not related to vinyl monomers and radical polymerization. The first one is the ring-opening polymerization of e-caprolactone in dioxane-heptane (30). A graft copolymer, poly(dodecyl acrylate)-g-poly(e-caprolactone), is used as a stabilizer. The polymerization proceeds via anionic or pseudoanionic mechanism initiated by diethylaluminum ethoxide or other catalysts. The size of poly(caprolactone) particles depends on the composition of stabilizer, ranging from 0.5 to 5 i,m. Lactide was also polymerized in a similar way. Poly(caprolactone) and poly(lactide) particles with a narrow size distribution are expected to be applied as degradable carriers of drugs and bioactive compounds. 

When a miniemulsion polymerization initiated by Co y-rays was carried out to synthesize polystyrene particles [65], the dose rate and total dose were each found to aflect the size of the latex particles. Y-Hke branched surfactants were synthesized and used for y-ray miniemulsion polymerization at room temperature [66] moreover, 2wt% polyurethane used as a hydrophobe for the miniemulsion polymerization of styrene was suflBdent to ensure a shelf-Hfe of one year for the miniemulsion [67]. In both cases [66, 67], the particle size and distribution were preserved throughout the polymerization. The copolymerization of styrene with l-vinyl-2-pyrrolidone as a polar monomer in the presence of dodecane in the oil droplets, also led to the production of nanocapsules [68]. Subsequent H NMR spectroscopic analyses showed that graft copolymers had been obtained via radiation-induced polymerization, rather than random copolymers. Hence,... 

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