PDMAEMA-b-PLMA-b-POEGMA triblock terpolymers via RAFT polymerization and their self-assembly in aqueous solutions†
We report the synthesis, quaternization and self-assembly in aqueous media of novel amphiphilic and pH responsive triblock terpolymers of the type poly[2-(dimethylamino)ethyl methacrylate-b-lauryl methacrylate-b-(oligo ethylene glycol)methacrylate] (PDMAEMA-b-PLMA-b-POEGMA). The terpolymers were synthesized by RAFT polymerization and molecularly characterized by SEC, 1H-NMR and FTIR spectroscopy. Methyl iodide was used for quaternization of the PDMAEMA blocks, in order to increase the solubility of the terpolymers in water and to impart a permanent positive charge, transforming them to amphiphilic block polyelectrolytes. PDMAEMA-b-PLMA-b-POEGMA and QPDMAEMA-b-PLMA-b-POEGMA terpolymers self-assemble into spherical micelles in aqueous media, as indicated by light scattering and scanning electron microscopy results. The dimensions of the micelles were not affected appreciably by changes in the pH of the solutions, an observation attributed to crowding within the mixed PDMAEMA/POEGMA corona. QPDMAEMA-b-PLMA-b-POEGMA terpolymer micelles were found to dissociate by an increase of ionic strength, due to the collapse of the QPDMAEMA blocks and as a result of the low Tg of the PLMA core block.