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

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 approximate to 57 to approximate to 390 nm, conversions up to approximate to 96%, nitroxide efficiencies (N-Eff) up to approximate to 0.76, and number average molecular weight (M-n) ranging from approximate to 10 000 to approximate 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.

Automated summary

Stable polystyrene latexes with controlled molecular weight distribution are obtained by using efficient TEMPO oxidants in combination with nitroxides as initiators. Different concentrations of styrene lead to colloidal dispersions with adjustable particle size, conversion rates, and molecular weights.