Self-Assembly Behavior of Triphilic Diblock Copolymer Blends

A series of triphilic diblock copolymer blends, consisting of hydrophilic poly(ethylene glycol) monomethyl ether (PEG), hydrophobic polystyrene (PS) and superhydrophobic poly(1H,1H,5H-octafluoropentyl methacrylate) (POFPMA), were blended with two diblock copolymers PEG-PS and PEG-POFPMA. The two copolymers were successfully synthesized by atom transfer radical polymerization (ATRP) and single electron transfer living radical polymerization (SET-LRP), and were characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). Hydrophobic segments have been regarded as one of the most important limited factors for the preparation of nano-assemblies in aqueous solution. The transformation of a series of PEG-PS/PEG-POFPMA nano-assemblies were investigated by changing the polymerization degree of hydrophobic PS and superhydrophobic POFPMA, which were confirmed by dynamic light scattering (DLS), transmission electron microscope (TEM) and scanning electron microscopy (SEM). The results indicated that adjusting the ratio of the double hydrophobic blocks was an effective way to obtain rich assembled morphologies of the triphilic diblock blends, including spherical micelles, porous spheres, vesicles, spindle-like micelles and worm-like micelles. In addition, self-assembly based on one typical blend at different concentrations was also investigated, and it was obvious that the morphology evolved from the porous sphere to the coil structure, then to vesicle with the increase of concentration. The assembled morphologies of the blends changed from strip micelles to dendritic micelles, vesicles and porous spheres, and eventually led to the formation of spherical micelles by increasing the length of PS, but they were mainly affected by low concentration of the blends. Two detailed and regular binary phase diagrams based on the above results were concluded and served as a reliable reference for targeting predetermined nanoparticles before polymerization.