Semibatch Emulsion Polymerization Using TIPNO and the Universal Alkoxyamine

Three bicomponent initiation systems, consisting of 2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) and one of the initiators potassium persulfate (KPS), benzoyl peroxide (BPO), or 2,2’-azobis(isobutyronitrile) (AIBN), were used to develop a robust and versatile semibatch emulsion polymerization process to obtain polystyrene (PS) latexes with solids up to 40 wt % . The alkoxyamine of TIPNO was also used as a macroinitiator to prepare stable and controlled latexes of PS, poly(n-butyl methacrylate) (PnBMA), poly(n-butyl acrylate) (PnBA), poly(2-ethylhexyl acrylate) (PEHA), and the copolymer PS-b-PnBA with solids contents up to nearly 40 wt %. Using different concentrations of styrene (St) in the nucleation step and by varying the monomer feed rate, it was possible to obtain colloidal dispersions with particle sizes ranging from ∼80 to ∼300 nm, conversions up to ∼97.0%, nitroxide efficiencies (NEff) up to ∼1.00 and number-average molecular weights (Mn) from ∼46,000 to ∼102,000 g/mol. These polymerizations were conducted using a simple and rapid process, similar to industrially used conditions, as the seed is formed in situ during the heating ramp and the initial stage of the polymerization.