Studies on the mechanism for the formation of the stable dispersion polystyrene prepared by anionic dispersion polymerization of styrene in n-hexane using poly(t-butylstyrene) as the stabilizing moiety in steric stabilizer have been performed by a combination of size exclusion chromatographic (SEC) and transmission electron microscopic (TEM) analyses. When the molecular weight of poly(t-butylstyrene) as the stabilizing moiety exceeded 1.76 X lo4 g/mol, the formed polymer particles successfully retained a steric stability. Block copolymerization of t-butylstyrene and styrene in n-hexane has also provided the dispersion polymer particles with a relatively narrow size distribution. The stable dispersion polystyrenes have been produced in n-hexane by polymerization of styrene using the mixture of sec-butyllithium and poly( t-butylstyry1)lithium. The polymerization is called living dispersion polymerization (LDP), in which poly(t-butylstyrene-b-styrene) as the steric stabilizer and polystyrene can be formed simultaneously. The particle size was readily controlled by a combination of the concentration of monomer and the molar ratio of poly(t-butylsty-ry1)lithium to sec-butyllithium, for instance, [stabilizing moiety]/[RLi]. 0 1996 John Wiley & Sons, Inc.