Synthesis and Micellization Properties of Double Hydrophilic A2BA2and A4BA4Non-Linear Block Copolymers

We describe the first account of the synthesis and intriguing micellization properties of nonlinear double hydrophilic block copolymers (DHBCs) of the A 2 BA 2 and A 4 BA 4 type. Atom transfer radical polymerization (ATRP) macroinitiators with two and four initiating sites at both ends of poly(propylene oxide) (PPO) chain were synthesized via reacting 2-hydroxyethyl acrylate and glycidol with commercially available diamine-terminated PPO, respectively, followed by esterification with excess 2-bromoisobutyryl bromide or 2-bromopropionyl bromide. Well-defined nonlinear DHBCs, (PDEA) 2 PPO(PDEA) 2 (H-shaped) and (PDEA) 4 PPO(PDEA) 4 (star- b -linear- b -star), were then prepared by polymerizing 2-(diethylamino)ethyl methacrylate (DEA) via ATRP in 2-propanol at 40 °C using the prepared macroinitiators, where PDEA was poly(2-(diethylamino)ethyl methacrylate). The structures of the resulting nonlinear shaped copolymers were characterized by 1 H NMR and gel permeation chromatography (GPC). The pH- and thermoresponsive micellization behavior of (PDEA 10 ) 2 PPO(PDEA 10 ) 2 and (PDEA 11 ) 4 PPO(PDEA 11 ) 4 was then investigated by a combination of dynamic laser light scattering (LLS) and fluorescence techniques. Compared to the linear counterpart, the nonlinear block copolymers exhibited complex and interesting micellization properties.