Converse transitions between the micelles and the vesicles of pyrrolidone-based AIE amphiphilic copolymers in polar and apolar solvents.

Herein, a new family of aggregation-induced emission (AIE) amphiphilic copolymers, named poly( N -(2-methacryloyloxyethyl)pyrrolidone)- b -poly(lauryl methacrylate- co -1-ethenyl-4-(1,2,2-triphenylethenyl)benzene), PNMP x - b -P(LMA y - co -TPE z ), was developed by the reversible addition-fragmentation chain transfer (RAFT) polymerization method. The polymerization degree x of the NMP segment was kept constant at 35, whereas that of the LMA segment ranged from 9 to 55 with the polymerization degree ratio y / z of the LMA and TPE segments being around 9. As a result, the PNMP x - b -P(LMA y - co -TPE z ) copolymer gradually transformed from being water soluble to oil soluble with an increase in the length of the P(LMA y - co -TPE z ) segment. Moreover, these copolymers could form self-organized normal and reverse assemblies in both water and n -dodecane. Various morphologies, including spherical micelles, worm-like micelles and vesicles, were confirmed by the transmission electron microscopy (TEM) observation. Specifically, the micelle-to-vesicle transition via worm-like micelles occurred in the aqueous solution upon increasing the length of the P(LMA y - co -TPE z ) segment, whereas the reverse transition occurred in n -dodecane. Because of the presence of the AIE-active TPE segment, both the aqueous and the n -dodecane solutions of PNMP x - b -P(LMA y - co -TPE z ) were highly luminescent, and their fluorescence quantum yields significantly depended on the polarity of the solvent and the morphology of the assemblies. Due to the strong luminescence properties of PNMP x - b -P(LMA y - co -TPE z ) assemblies, these AIE-active amphiphilic copolymers acted as excellent bioimaging probes with high efficiency.