Synthesis and Aggregation Behaviors of Nonlinear Multiresponsive, Multihydrophilic Block Copolymers

The well-defined nonlinear multiresponsive, multihydrophilic block copolymers (MHBCs), poly( N -isopropylacrylamide) 2 −[poly( N -vinylpyrrolidone)- b -poly(acrylic acid)] 2 ((PNIPAAM) 2 (PNVP- b -PAA) 2 ) and poly[ N -isopropylacrylamide- b -(acrylic acid)] 2 −poly( N -vinylpyrrolidone) 2 ((PNIPAAM- b -PAA) 2 (PNVP) 2 ), were successfully synthesized via a combination of single-electron transfer living radical polymerization (SET-LRP) and reversible addition−fragmentation chain transfer (RAFT) polymerization techniques. All the final miktoarm star block copolymers were characterized by GPC and 1 H NMR spectra. Interestingly, the hydrogen bonding interactions have a great effect on the water solubility of PAA chains, and the nonlinear MHBCs solutions showed sharp phase separation at pH = 7.0. The novel water-soluble nonlinear MHBCs consisting of pH-responsive PAA segments, thermoresponsive PNIPAAM segments, and hydrophilic, noncharged and biocompatible PNVP segments tend to self-assemble into three different types of micellar aggregates and umimers, which can be reversibly controlled by pH value and temperature of aqueous solution of these copolymers.