Stimuli-responsive macroazoinitiators with central azo unit have been synthesized by atom transfer radical polymerization (ATRP) of 2-dimethylamino) ethyl methacrylate or 2-(diethylamino)ethyl methacrylate in 2-propanol at 25 degrees C. The mean degree of polymerization of the polymer chains besides the azo group was fixed between 25 and 60. H-1 NMR, gel permeation chromatography, UV-Vis spectrophotometer, and surface tensiometer were used to characterize the stimuli-responsive macroazoinitiators in terms of their chemical structure, molecular weight, polydispersity, and pH-responsive behavior, respectively. Eventually, dispersion polymerization of styrene using the poly[2-(diethylamino)ethyl methacrylate] (PDEA) macroazoinitiator as an inistab (initiator + stabilizer) in 2-propanol medium was conducted. Near-monodisperse 98 nm polystyrene (PS) latex particles with pH-responsive PDEA hair were successfully synthesized. The PS latex particles with the PDEA hair can be dispersed in acidic aqueous media where the PDEA hair was protonated and was solvated, and can be flocculated in basic aqueous media where the PDEA hair was deprotonated and was precipitated. This dispersion-flocculation cycle was reversible. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3431-3443, 2009