Additives Induced Structural Transformation of ABC Triblock Copolymer Particles

Abstract

Here we report the structural control of polystyrene-b-polyisoprene-b-poly(2-vinylpyridine) (PS-b-PI-b-P2VP) asymmetric ABC triblock copolymer particles under 3D confinement by tuning the interactions among blocks. The additives, including 3-n-pentadecylphenol, homopolystyrene, and solvents, which can modulate the interactions among polymer blocks, play significant roles in the particle morphology. Moreover, the structured particles can be disassembled into isolated micellar aggregates with novel morphologies or mesoporous particles with tunable pore shape. Interestingly, the formed pupa-like PS-b-PI-b-P2VP particles display interesting dynamic stretch-retraction behavior when the solvent property is changed after partial cross-linking of the P2VP block. We further prove that such dynamic behavior is closely related to the density of cross-linking. The strategies presented here are believed to be promising routes to rationally design and fabricate block copolymer particles with desirable shape and internal structure.

Self‐Assembly of Multiblock Copolymers

“…Since P2VP is known to be a very good hydrogen bond (HB) acceptor there are various possibilities for supramolecular modification of the volume of the P2VP microdomain and its interactions with other polymer blocks. Staying with the example of PS‐ b ‐PI‐ b ‐P2VP, the particle morphology was significantly influenced by additives including solvents, homopolymers (in both wet‐ and dry‐brush regime), and HB donor molecules (3‐ n ‐pentadecylphenol) . In addition, a pH‐triggered reversible morphology transition between pupa‐like particles and stretched pupa‐like particles was observed by slightly cross‐linking the P2VP block.…”

“…As the polymer architecture determines microphase separation, the resulting microparticle shape and morphology should be likewise affected when extending the process to ABC triblock terpolymers. Although interesting inner structure and functional microdomains are to be expected, 3D confinement assembly was rarely addressed in simulations or experiments . In MC simulations, a variety of unique nanostructures were identified beside the normal bud‐like and pupa‐like nanostructures by changing the solvent properties, incompatibilities between each block, and the symmetry of terpolymer.…”

“…In experiment, the confinement self‐assembly of ABC triblock terpolymer was only recently studied. In a first example, morphologies of PS‐ b ‐PI‐ b ‐P2VP triblock terpolymers were analyzed in confinement with respect to block weight fraction and the influence of the surfactant . For that, emulsions with different ratios of PVA (favorable for P2VP) and CTAB (favorable for PS and PI) were prepared.…”

“…Although interesting inner structure and functional microdomains are to be expected, 3D confinement assembly was rarely addressed in simulations [87,88] or experiments. [89,90] In MC simulations, a variety of unique nanostructures were identified beside the normal bud-like and pupa-like nanostructures by changing the solvent properties, incompatibilities between each block, and the symmetry of terpolymer. Self-consistent field theory (SCFT) mainly describes the conformation of the polymer chain during microphase separation; the component density distribution can be precisely described in an equilibrium state.…”

“…In a first example, morphologies of PS-b-PI-b-P2VP triblock terpolymers were analyzed in confinement with respect to block weight fraction and the influence of the surfactant. [89,90] For that, emulsions with different ratios of PVA (favorable for P2VP) and CTAB (favorable for PS and PI) were prepared. With increasing ratio of CTAB/PVA, particle shape and inner structure underwent a series of transformations: first the spherical microparticles exhibit a concentric lamella-lamellae morphology (onion-like) due to the equal weight fractions of PS/PI/P2VP with P2VP as outmost layer exposed to the surfactant/water phase; with addition of CTAB, the top half of the onion-like particle transformed into axially-stacked lamellae of PS/PI/P2VP giving the microparticle a "bud-like" shape.…”