TEMPO Mediated Radical Emulsion Polymerization of Styrene by Stepwise and Semibatch Processes

In the present study we carried out nitroxide mediated radical polymerizations (NMRP) of styrene in emulsion using 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) by stepwise and semibatch processes obtaining polystyrene (PS) with a dispersity (Đ) lower than 1.5 and average particle diameter (Dp) between 180 and 520 nm when methanol was used. Otherwise, when the polymerization was carried out in the absence of methanol, a bimodal particle size distribution (PSD) was obtained. This is attributed to the super‐swelling effect, which causes the particles to grow considerably and also to lower the nitroxide efficiency reducing chain formation and thus drastically reducing the particle nucleation. These polymerizations did not require a separate macroinitiator synthesis step, which represents an important simplification for further applications.