Well-defined N-Isopropylacrylamide Dual-Sensitive Copolymers with LCST ∼38 °C in Different Architectures: Linear, Block and Star Polymers

Reversible addition-fragmentation chain transfer (RAFT) polymerization is used to prepare temperature- and pH-sensitive statistical copolymers with lower critical solution temperature (LCST) close to 38 degrees C at pH 7.4 based on N-isopropylacrylamide and methacrylic acid derivative comonomers with a pKa close to 6. Statistical copolymers are re-activated to prepare amphiphilic block copolymers and star polymers with cross-linked core. The LCST is maintained by varying the architecture; however, the LCST originated behaviour changes due to self-aggregation. Statistical copolymers and short block copolymers show complex aggregation, whereas mid-size block copolymers and star polymers show shrinkage of aggregate dimensions. The pH of the medium has a profound impact on the self-assembling behaviour of the different polymer architectures.