Ordered Mesoporous Microcapsules from Double Emulsion Confined Block Copolymer Self-Assembly

Abstract

Polymeric microcapsules with shells containing homogeneous pores with uniform diameter on the nanometer scale are reported. The mesoporous microcapsules are obtained from confined self-assembly of amphiphilic block copolymers with a selective porogen in the shell of water-in-oil-in-water double emulsion drops. The use of double emulsion drops as a liquid template enables the formation of homogeneous capsules of 100s of microns in diameter, with aqueous cores encapsulated in a shell membrane with a tunable thickness of 100s of nanometers to 10s of microns. Microcapsules with shells that exhibit an ordered gyroidal morphology and three-dimensionally connected mesopores are obtained from the triblock terpolymer poly­(isoprene)-block-poly­(styrene)-block-poly­(4-vinylpyridine) coassembled with pentadecylphenol as a porogen. The bicontinuous shell morphology yields nanoporous paths connecting the inside to the outside of the microcapsule after porogen removal; by contrast, one-dimensional hexagonally packed cylindrical pores, obtained from a traditional diblock copolymer system with parallel alignment to the surface, would block transport through the shell. To enable the mesoporous microcapsules to withstand harsh conditions, such as exposure to organic solvents, without rupture of the shell, we develop a cross-linking method of the nanostructured triblock terpolymer shell after its self-assembly. The microcapsules exhibit pH-responsive permeability to polymeric solutes, demonstrating their potential as a filtration medium for actively tunable macromolecular separation and purification. Furthermore, we report a tunable dual-phase separation method to fabricate microcapsules with hierarchically porous shells that exhibit ordered mesoporous membrane walls within sponge-like micron-sized macropores to further control shell permeability.

Interfacial Assembly and Applications of Functional Mesoporous Materials

“…In addition, a tunable dual-phase separation method was used to fabricate microcapsules with hierarchically porous shells that exhibited ordered mesoporous membrane walls within sponge-like micrometer-sized macropores to further control shell permeability. As a result, The microcapsules showed pH-responsive permeability to polymeric solutes, demonstrating their potential as a filtration medium for actively tunable macromolecular separation and purification . This strategy using double emulsion droplets to create microscale interfaces provides a new route to design and synthesize mesoporous materials with multileveled structures.…”

Monodispersed polymer particles with tunable surface structures: Droplet microfluidic‐assisted fabrication and biomedical applications

“… 41 In another example, highly ordered mesoporous microcapsules of BCPs were reported by Weitz et al through solvent treatment (Figure 5C). 42 A hydrogen‐bond donor, n ‐pentadecyl phenol (PDP), was employed as the porogen. Microcapsules of BCP were prepared by using W/O/W double emulsion droplets as templates.…”

“…(A) Schematic illustration of porous polymer particles prepared by postprocessing. (B–D) porous particles prepared by solvent treatment of porogens: (B) decyl alcohol (DA), 41 (C) pentadecylphenol (PDP) 42 and (D) PVP K30 43 . Reprinted with permission from References 41 and 43.…”

“…Poly(-HEMA-MMA) microspheres with PVP porogen inside were prepared by using UV photopolymerization of O/W F I G U R E 5 (A) Schematic illustration of porous polymer particles prepared by postprocessing. (B-D) porous particles prepared by solvent treatment of porogens: (B) decyl alcohol (DA), 41 (C) pentadecylphenol (PDP) 42 and (D) PVP K30. 43 emulsion droplets, and then porous particles were generated by rinsing preformed particles in water to dissolve PVP K30 (Figure 5D).…”

Modified Breath Figure Methods for the Pore-Selective Functionalization of Honeycomb-Patterned Porous Polymer Films

“…These properties make them highly desirable for potential applications such as antibacterial membranes [ 4 , 5 ], microelectronics [ 6 ], sensors [ 7 , 8 , 9 , 10 , 11 ], cell culture scaffolds [ 12 , 13 ], superhydrophobic surfaces [ 14 , 15 ], and size-selective separators [ 16 ]. These films can be obtained either via top-down lithographic techniques, such as photo-lithography [ 17 ] and contact lithography, or bottom-up fabrication such as self-assembly mechanisms of colloidal particles [ 18 , 19 ], emulsions [ 20 , 21 ], block copolymers [ 22 , 23 ], and phase separation [ 24 , 25 ]. Although the lithography process can reliably fabricate high-ordered porous films with a constant pattern, they usually require multiple processing steps and pre-patterned templates making the overall process tedious.…”