Synthesis of Poly(2-ethyl-2-oxazoline)-<i>b</i>-poly(styrene) Copolymers via a Dual Initiator Route Combining Cationic Ring-Opening Polymerization and Atom Transfer Radical Polymerization

Block copolymers of 2-ethyl-2-oxazoline (EtOx) and styrene were synthesized by a combination of cationic ring-opening polymerization (CROP) and atom transfer radical polymerization (ATRP). Initially, a detailed kinetic investigation for the α-bromoisobutyrylbromide (BrEBBr) initiated CROP of EtOx was performed in acetonitrile at different polymerization temperatures ranging from 100 to 180 °C under microwave irradiation. Poly(2-ethyl-2-oxazoline) (PEtOx) homopolymers with controlled molecular weights and narrow polydispersity indices were synthesized in short reaction times. Polymers with relatively high molar masses and low polydispersity indices (Mn,SEC = 48 500 g/mol, PDI = 1.29) could also be obtained. Following the synthesis of a PEtOx macroinitiator (Mn,SEC = 3700 g/mol, PDI = 1.09), the ATRP of styrene was performed with CuBr and tris[2-(dimethylamino)ethyl]amine (Me6Tren) as catalytic system. The micellization behavior of the obtained amphiphilic block copolymers was further investigated by dynamic light scattering (DLS) and atomic force microscopy (AFM).