Morphology transition of amphiphilic homopolymer self-assemblies in water triggered by pendant design and chain length

In this paper, we examined self-assembly of amphiphilic homopolymers bearing the double brush side chains of a hydrophilic PEG and various hydrophobic units including butyl, octyl, dodecyl, octadecyl, and oleyl groups in water. Analyzed by size exclusion chromatography coupled with multiangle laser light scattering, those homopolymers formed uniform micelles, unimer micelles, and large aggregates like rod micelles in water; the morphology depended on the hydrophobic side chains and changed at a certain threshold degree of polymerization (DPth). The homopolymer comprising butyl groups folded into compact micelles via intramolecular association in water, independent of molecular weight. In contrast, the homopolymer carrying octyl groups formed either uniform micelles via multichain association ( < DPth) or unimer micelles via single chain folding ( > DPth). The homopolymers carrying dodecyl, octadecyl, and oleyl groups exclusively undergo multichain association in water but form either uniform micelles ( < DPth) or large aggregates ( > DPth). Uniquely, those DPth values decreased with increasing the hydrophobicity of the pendants; more hydrophobic homopolymers tend to form large aggregates at shorter polymer chains. Additionally, those homopolymers with broad molecular weight distribution induced chain length-dependent self-sorting to simultaneously produce uniform micelles and large aggregates in water.