Synthesis and Aggregation Behaviors of Well-Defined Thermoresponsive Pentablock Terpolymers With Tunable LCST

A series of thermoresponsive pentablock terpolymers, poly(N-isopropylacrylamide)-b-poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(N-isopropylacrylamide), is prepared by reversible additionfragmentation chain transfer (RAFT) polymerization. The effect of NIPAM and PPO block lengths on lower critical solution temperature (LCST), critical micelle concentration (cmc), and aggregation number (Nagg) is investigated via UVVis spectroscopy and steady-state fluorescence spectroscopy. The results show that upon increasing the block lengths, LCST and cmc decrease, while Nagg increases. TEM observation shows that associated spherical-like particles are evidenced below the LCST of the terpolymers, and regular or irregular spherical micelles or even intermicellar aggregates are observed above the LCST.