Synthesis of amphiphilic polystyrene–ionene diblock copolymers with controlled block lengths

Amphiphilic polystyrene-ionene diblock copolymers with blocks of controlled molecular weights were synthesized by a new method. The preparation starts with the anionic polymerization of styrene with 3-(dimethylamino)propyl-lithium as initiator, yielding tertiary amino end-functionalized polystyrenes of molecular weights that can be varied over a wide range from 1 to 100kg/mol, and a relatively low polydispersity (M?_w/M?_n = 1.1–1.4). The crucial step in this method is the stepwise coupling of the reactive end-group of the polystyrene with bromo- and tertiary-amino-terminated monodisperse oligomeric 2,4-ionenes. The amphiphilic polymers with well-defined block lengths were characterized by thin-layer chromatography, end-group titration and elemental analysis. Amphiphilic block copolymers with a monodisperse ionene block consisting of up to 10 quaternary ammonium groups could be derived.