Pathway-dependent re-assembly of dual-responsive ABC terpolymer in water

Abstract

A poly(ethylene glycol)-b-poly(n-butyl methacrylate)-b-poly(N,N′-dimethylamino ethyl methacrylate) (PEG-b-PnBMA-b-PDMAEMA) triblcok terpolymer with a dual pH- and thermo-responsive PDMAEMA as end segment was prepared via sequential RAFT polymerization. The PEG-b-PnBMA-b-PDMAEMA self-assembled into spherical micelles in acidic solution but transformed into cylindrical micelles in alkaline solution. This pH induced re-assembly was reversible. Moreover, we found that this terpolymer underwent a pathway dependent re-assembly from cylinder to toroid or to vesicle upon programmed variation of solution pH and temperature in dilute aqueous solution. Using dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryoTEM), we found that this stimuli-induced re-assembly from cylinder to toroid or to vesicle was apparently irreversible, and restoration of pristine morphology only happened using different external stimulus. Our studies demonstrated a prototype of smart supramolecular assembly that we can re-assembly into different micelle morphologies using different stimuli.