Self-Sorting of Amphiphilic Block-Pendant Homopolymers into Sphere or Rod Micelles in Water

The autonomous and simultaneous construction of discrete nanoobjects via the self-assembling process is a challenging issue in materials chemistry and science. Here, we report self-sorting systems of amphiphilic block-pendant homopolymers via precision self-assembly into sphere or rod micelles in water. For this, we designed an amphiphilic block monomer, N,N'-disubstituted acrylamide, with a hydrophilic poly(ethylene glycol) (PEG) and a hydrophobic and crystalline octadecyl group. In water, the homopolymers of this monomer efficiently induce self-sorting via multichain self-assembly to simultaneously form core-crystalline sphere or rod micelles in water. Critically dependent on the chain length (degree of polymerization: DP), the homopolymers shorter than a threshold DP selectively formed uniform spherical micelles; the uniformness was better than that of the spherical micelles of corresponding random copolymers. In contrast, the homopolymers longer than the threshold DP formed rod micelles, whose size dramatically increased with increasing DP. Such DP-dependent self-sorting into sphere or rod micelles was characteristic of the amphiphilic block-pendant homopolymers, since sphere or necklace micelles were obtained from corresponding amphiphilic random copolymers in water, dependent on DP. The mixture of the homopolymers and the random copolymers further afforded complex self-sorting to simultaneously provide sphere, necklace, and rod micelles in water.