Hierarchical Assembly of Complex Block Copolymer Nanoparticles into Multicompartment Superstructures through Tunable Interparticle Associations



A challenging aim in both materials physics and chemistry is the construction of complex and functional superstructures from designed nanoscale building units. Block copolymer nanoparticles with morphological variety and compositional complexity have been made with solution-based assembly. However, routine ability to build hierarchical superstructures by inter-nanoparticle association is not yet possible. A hierarchical assembly strategy of organizing pre-formed spherical block copolymer nanoparticles into superstructures, including linear, circular, and close-packed arrays, via tunable interparticle interactions is presented. Solution-state mixtures are made of two amphiphilic diblock copolymers, poly(acrylic acid)-block-poly(methyl methacrylate) (PAA-b-PMMA) and poly(acrylic acid)-block-polybutadiene (PAA-b-PB) with additional crown ether functionalities grafted onto 40 mol% of the AA repeat units on the PAA-b-PMMA diblock copolymer. Through kinetic control of the solution assembly process in aqueous/N,N-dimethylformamide (DMF) mixtures (4:1 water:DMF), spherical nanoparticles with compositional complexity confined in both the core and shell are obtained. Benefiting from host-guest chemistry, interparticle association is triggered and tuned by the addition of di-functional organoamines due to amine-crown ether complexation. The resultant multiparticle superstructures contain well-defined multicompartments within individual, constituent nanoparticles due to the local separation of unlike PB and PMMA hydrophobic blocks within the cores of the individual particles. Through competitive complexation with potassium ions, the superstructures are disassembled into individual multicomparment nanoparticles.