Effects of polystyrene-b-poly(aminomethyl styrene)s as stabilizers on dispersion polymerization of styrene in alcoholic media.

The effects of polystyrene-b-poly(aminomethyl styrene) (PS(n)-b-PAMS(m)) stabilizers on the particle size (D(n)) and size distribution (PSD) in dispersion polymerization of styrene were investigated. The block copolymers, PS(n)-b-PAMS(m), were prepared as follows: (i) atom transfer radical polymerization (ATRP) of styrene (PS-Br), (ii) ATRP of vinylbenzylphthalimide with the PS-Br (PS-b-PVBP), and (iii) treatment of the PS-b-PVBP with hydrazine. When the dispersion polymerization of styrene proceeded at 60 degrees C in ethanol with PS(19)-b-PAMS(130) stabilizer, spherical polystyrene particles with D(n)=0.91 microm (PSD=1.01) were obtained. The particle size was strongly affected by the copolymer composition. With an increase in PAMS block length from m=54 to 100 in PS(17)-b-PAMS(m), particle diameter became smaller from 1.55 to 0.91 microm. On the other hand, an increase in the length from m=20 to 82 in PS(34)-b-PAMS(m)s caused an increase in particle size from 0.35 to 0.70 microm. Titration of the particles suggests that 14-81% of stabilizers used in the polymerization system were attached on the polystyrene particle surfaces, depending on the composition of the block copolymers. Thus, for the dispersion polymerization of styrene, PS(n)-b-PAMS(m) block copolymers have both functions as a stabilizer during polymerization and surface-modification sites of polystyrene particles.