Micellar Self-Assembly and Probe Exchange Dynamics of Triblock Copolymer Poly(ethylene oxide)–Poly(propylene oxide)–Poly(ethylene oxide) PEO57PPO45PEO57

The dynamics of micellar solutions of a triblock poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) copolymer, PEO57PPO45PEO57 where the subscripts indicate the block length, has been analyzed. This copolymer is characterized by a large monodispersity and hydrophilicity if compared to the previously studied commercially available Pluronic block copolymers. Different experimental techniques were used to characterize its micellar self-assembly, elucidating the existence of a concentration-dependent transition to a “pseudo-percolated” state as the temperature increases in which interconnected polymeric micelles are formed. The kinetics of the micellar assembly and disassembly processes and solute exchange dynamics were monitored by stopped-flow time-scan fluorescence measurements using a fluorescent probe, which points to the involvement of several underlying mechanisms other than simple particle collisions: a slow dynamic regime below 45 °C; a transition regime between 45 and 50 °C; and a fast ...