Influence of selective solvents on self-assembly behaviors of amphiphilic hyperbranched poly(aryl ether ketone)-graft-poly(ethylene glycol) rod–coil copolymer

Abstract

An amphiphilic hyperbranched poly(aryl ether ketone)- graft-poly(ethylene glycol) (HPAEK- graft-PEG) rod–coil copolymer was synthesized by grafting linear PEG onto hydroxyl-terminated HPAEK (OH-HPAEK). The molecular structure, the number-average molecular weight and the thermal properties of HPAEK- graft-PEG were characterized by proton nuclear magnetic resonance and Fourier transform infrared spectroscopies, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis, respectively. The self-assembly behaviors of HPAEK- graft-PEG in the mixed solvents were investigated by transmission electron microscopy and scanning electron microscopy. The results demonstrated that the selective solvent in the used mixed solvents exerted remarkable influence on the morphology of the resulting micelles. When the mixed solvents were water/tetrahydrofuran (THF), trichloromethane/THF, and toluene/THF, that is, with the decrease of the selective solvents in polarity, HPAEK- graft-PEG could self-assemble into the regular microspheres with obvious core–shell structure, the similar quadrilateral-shaped micelles with the dimension of about 20 nm and the large complicated clew-shaped micelles, as well as the irregular large compound micelles, respectively. It is worth mentioning that the similar quadrilateral-shaped micelles were different from the toroidal micelles reported already, which had relatively obvious “angle”. The phenomenon may be ascribed that the rigid characteristic of rod HAPEK segment was conducive to the maintenance of the metastable state.

“Rod–coil” copolymers get self-assembled in solution

“…1). [213][214][215] The unique structure makes the rod-coil hyperbranched copolymers form unimolecular micelles easily, [216][217][218] which may further self-assemble into large micelles without phase separation through a ''multi-micelle aggregate'' (MMA) mechanism. [219][220][221] This merit favors the fluorescence emission of aggregation-caused quenching molecules in their aggregates.…”