Emulsifier-free emulsion polymerization of the comonomer system styrene/tetrahydrofurfuryl metacrylate

The emulsifier-free emulsion copolymerization of styrene and tetrahydrofurfuryl methacrylate (TMA) in aqueous phase is described. Monidisperse latex particles with diameters from about 280 to 620 nm are obtained consisting of a hydrophobic polystyrene core and a hydrophilic poly-TMA shell. The influence of a variation of TMA, styrene and initiator (potassium persulfate) concentration in the original emulsion on particle size, molecular weight and composition of the copolymer is described. The concentration of TMA and initiator affects the number of primary particles but not the size of the final particles, whereas the styrene concentration strongly influences the particle diameter, a large size being favored by a high styrene concentration. The molecular weights of the polymers are between 6.2×104 and 7.0×105 g/mole. Size exclusion chromatography of polymer solutions in tetrahydrofuran shows that high molecular weights are especially found in large particles, which are preferentially formed in emulsions with a high concentration of styrene. 1H-NMR spectroscopy of the polymer shows that only about 50% of the initial TMA concentration are polymerized in the particles. Thus the copolymers prepared at increasing styrene concentration and constant initiator concentration of the emulsion show an increasing polystyrene content and are formed in particles of increasing size.