Multicompartment Nanoparticles Bearing Hydrophilic/Hydrophobic Subdomains by Self-Assembly of Star Polymers in Aqueous Solution

The direct construction of protein-like multicompartment nanoparticles (MCNs) possessing hydrophilic/hydrophobic subdomains is a contemporary challenge. Herein, we present the first example of such MCNs via self-assembly of the specially designed A(BC)20 star polymer in an aqueous solution. The topology of the 21-arm star polymer, poly(ethylene glycol)[poly(acrylic acid)-block-polystyrene]20 [PEG(PAA-b-PS)20], is the key to simultaneously form hydrophilic/hydrophobic subdomains of nanoparticles during self-assembling, as the water-soluble PAA blocks are confined in the core, resulting in hydrophilic subdomains. The volume ratio of PS to PAA (VPS/VPAA) is found to be the main factor that determines the morphology of MCNs; besides micelles and vesicles, strings consisting of one-dimensional (1D) alignment of single-star polymers were found for the first time, as confirmed by transmission electron microscopy (TEM) and cryo-TEM. Lastly, a new mechanism for the assembly of the star polymers was proposed based on the investigations of PEG(PAA-b-PS)20 self-assembly under different water contents, concentrations, and pH values. The MCNs reported in this work may find various applications in, e.g., co-delivery of drugs and heterogeneous catalysis.