Synthesis of double-hydrophilic BAB triblock copolymers via RAFT polymerisation and their thermoresponsive self-assembly in water

Triblock copolymers of poly(N-isopropylacrylamide)-block-poly(N,N-dimethylacrylamide)-block-pol y(N-isopropylacrylamide) were synthesised via RAFT polymerisation using a symmetrical bistrithio carbonate. Keeping the block length of the permanently hydrophilic middle block constant, the length of the poly(N-isopropylacrylamide) block was varied broadly. The thermoresponsive aggregation of the polymers in water was studied by H-1 NMR, turbidimetry, and dynamic light scattering. The complex aggregation behaviour was block length dependent and occurred under kinetic control. Importantly, different information on the hydrophilic-hydrophobic transition of the poly(N-isopropylacrylamide) block was obtained using the various analytical methods and could not be directly correlated.