Deciphering the Influence of Zwitterionic Surfactants\non Pluronic Co-assemblies: A Synergistic Odyssey through Spectroscopic,\nMicroscopic, and Scattering Techniques

Fundamental investigations into the\nphotophysical properties and\nmicroenvironmental features of pluronic–zwitterionic surfactant\nmixed assemblies are essential for advancing our understanding of\nmolecular interactions at the nanoscale, setting the stage for innovative\nsolutions in drug delivery, diagnostics, and other applications of\npluronic–zwitterionic surfactant assemblies. This investigation\nexplores the intricate photophysics of pluronic–zwitterionic\nsurfactant mixed assemblies, utilizing the twisted intramolecular\ncharge transfer state forming styryl dye trans-2-[(4-dimethylamino)\nstyryl] benzothiazole as a probe. By comparing the behaviors of two\ndistinct poly(ethylene oxide)-<i>block</i>-poly(propylene\noxide)-<i>block</i>-poly(ethylene oxide) block copolymers\nwith block composition of (PEO)<sub>132‑</sub>(PPO)<sub>50</sub>-(PEO)<sub>132</sub> [F108] and (PEO)<sub>100</sub>-(PPO)<sub>65</sub>-(PEO)<sub>100</sub> [F127] at concentrations of 5 and 10 wt %, this\nstudy systematically examines the impact of the addition of zwitterionic\nsurfactants. Through a comprehensive set of analytical techniques,\nincluding UV–visible absorption, steady-state emission, and\ntime-resolved fluorescence emission studies, significant alterations\nin the emission spectra and quantum yields were observed upon the\naddition of zwitterionic surfactants. These modifications suggest\na dynamic equilibrium for the transitioning of dye molecules between\nvarious microenvironments within the assemblies. Additionally, dynamic\nlight scattering, zeta potential (ζ), nuclear Overhauser effect\nspectroscopy, small-angle neutron scattering, cryogenic transmission\nelectron microscopy, field emission scanning electron microscopy,\nand fluorescence lifetime imaging microscopy analyses have shed light\non the substantial impact of surfactant incorporation on the structural\nproperties of assemblies.