Synthesis and surface properties of amphiphilic star-shaped and dendrimer-like copolymers based on polystyrene core and poly(ethylene oxide) corona

Polystyrene (PS)/poly(ethylene oxide) (PEO) amphiphilic star-block copolymers and dendrimer-like architectures were prepared using a core-first method. PS stars were first obtained by atom transfer radical polymerization using three and four functional benzyl halides. The chain ends of these star polymers were subsequently modified to generate either the same or twice the number of hydroxyl groups that served to grow the PEO blocks by anionic polymerization of ethylene oxide. Well-defined PS_n-b-PEO_n (n = 3 or 4) stars and PS₃-b-PEO₆ dendrimer-like copolymers exhibiting a monomodal and narrow molar mass distribution were obtained in this way. When spread at the air/water interface, these stars proved to be surface active, forming stable reproducible films. Isotherms yielded A₀ (theoretical surface area occupied by a film at zero pressure) values, allowing for quantitative comparisons between the stars and linear diblock analogues. Both structures demonstrated similar behavior, passing from liquid expanded regins to highly compressed structures at comparable molecular areas.