Synthesis and polyelectrolyte behavior of poly(methacrylic acid) star polymers

Poly( tert ‐butyl methacrylate) [P( t BMA)] star polymers were synthesized by copolymerization of p( t BMA) macroinitiator with ethylene glycol dimethacrylate via atom transfer radical polymerization method. P( t BMA) stars had a narrow molecular weight distribution ( M w / M n = 1.06–1.15). The ratio of radius of gyration to hydrodynamic radius R G / R H , which indicates inner segment density, was in the range 1.16–1.22 in tetrahydrofuran (THF) (arm number f = 25–142). These stars behaved not as hard spheres but as soft spheres in THF. Poly(methacrylic acid) stars were obtained by the hydrolysis of P( t BMA) arms. We investigated the conformation of star polyelectrolyte as a function of pH and ionic strength by means of dynamic light scattering (DLS). The hydrodynamic diameter increased gradually from 18.8 to 48.3 nm as a function of the solution pH. In addition, we compared experimental results with theoretical models for star polyelectrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007