High Solids Hydroxy‐TEMPO Mediated Radical Semibatch Emulsion Polymerization of Styrene

Abstract Stable polystyrene latexes having controlled molecular weight distribution (MWD) with solids contents up to 40 wt% are obtained using potassium persulfate as initiator with the nitroxides 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐ N ‐oxyl (hydroxy‐TEMPO) and 4‐amino‐2,2,6,6‐tetramethylpiperidine‐ N ‐oxyl (amino‐TEMPO). Using different concentrations of styrene (St) in the nucleation step, it is possible to create colloidal dispersions with particle size ranging from ≈57 to ≈390 nm, conversions up to ≈96%, nitroxide efficiencies ( N Eff ) up to ≈0.76, and number average molecular weight ( M n ) ranging from ≈10 000 to ≈85 000 g mol −1 . The effect of the monomer feed rate in the semibatch step is also studied. These polymerizations do not require a separate macroinitiator synthesis, since this is formed in situ during the heating ramp. A mathematical model is used to compare the mechanistic understanding of the system with the experimental results.