Multi-Scale Nanostructures Based on Emulsion-Confined Self-Assembly of Degradable Block Copolymers

Emulsion-confined self-assembly of block copolymers (BCPs) provides an effective approach to the synthesis of polymer particles with different morphologies. In this research, emulsion-confined self-assembly of degradable BCPs is studied, and different nanosized objects are generated by using the degradable polymer particles as templates. Polystyrene- block -poly(4-vinylpyridine- co - n -butyl lipoate) (PS- b -P(4VP- co - n BuLp)) BCPs with cleavable disulfides in the P(4VP- co - n BuLp) block backbones were synthesized by two-step reversible addition–fragmentation chain-transfer polymerization. The BCPs make emulsion-confined self-assemblies into onion-like lamellar structures. Upon cleavage of the disulfides in acidic water, multilayered nanosheets are generated. Under ultrasonic treatment, the multilayered nanosheets are exfoliated, and isolated nanosheets are obtained. The addition of P(4VP- co - n BuLp) copolymer or PS homopolymer in the confined self-assemblies of BCPs can regulate the volume percentages of the components and the morphology of the BCP particles. With an increase in the content of the added polymers, structural transformations from onion-like lamellae to cylinders/spheres and to spheres are observed. By using the polymer particles as templates, nanosized objects, including nanosheets, cylinders, spheres, and hierarchical porous structures, are generated after the cleavage of the disulfide bonds in the polymer backbones.