Control of lengths and densities of surface-attached chains on polymer particles prepared by dispersion polymerization using macromonomer stabilizer

This study reported the control of molecular weights of functional polymer chains attached to the surfaces of the narrowly distributed environmentally responsive particles obtained from a single step process. As a proof-of-concept, a pH-responsive poly( l -glutamic acid) (PLGA) macromonomer with a degree of polymerization (n) of 50 or 260 was prepared by the ring-opening polymerization of γ-benzyl- l -glutamate N-carboxy anhydride; this was performed using 4-vinylbenzylamine and was followed by hydrolysis. The pH-responsive PLGA macromonomer was further used as a stabilizer for the dispersion polymerization of styrene. Each macromonomer stabilized the dispersion polymerization, affording narrowly distributed polystyrene particles exhibiting pH-responsive aggregation or dispersion behavior, thereby indicating the graft of PLGA chains on the particle surface. Large particles with a low surface density were obtained using PLGA260. The particle sizes and surface glutamic acid densities were tunable over 0.8–2.0 μm and 0.4–1.8 unit/nm2, respectively, while maintaining narrow size distributions.