Amphiphiles Coordinated to Block Copolymers as a Template for Mesoporous Materials

Abstract

We show a concept where coordination of amphiphiles to one block of a block copolymer leads to polymeric supramolecules and self-organization and that mesoporous materials can be achieved with a dense set of polymer brushes at the surfaces upon cleaving the amphiphiles by extraction with a selective solvent. Polystyrene-block-poly(4-vinylpyridine) (PS-block-P4VP) is used with zinc dodecylbenzenesulfonate (Zn(DBS) 2) which can coordinate to the lone electron pairs of the pyridine nitrogens in the P4VP block, leading to complexes PS-block-P4VP[Zn(DBS)2]y. Coordination of Zn(DBS)2 and structure formation were investigated using Fourier transformation infrared spectroscopy (FTIR), small-and wideangle X-ray scattering (SAXS and WAXS), and transmission electron microscopy (TEM). Lamellar structure was observed and even points toward a structural hierarchy for high molecular weight block copolymers. FTIR, SAXS, and TEM showed that most of Zn(DBS) 2 can be extracted from such templates using methanol, leading to lamellar porous structures. P4VP brushes cover the resulting pore surfaces. The structures do not collapse probably due to the glassy PS and defects in the nonaligned structure. Compared to hydrogen bonding, coordination allows bonding of higher molecular weight amphiphiles due to the stronger attraction.

Supramolecular routes towards liquid crystalline side-chain polymers

“…76 The advantage of using the metal coordination rather than the simple H-bonding discussed earlier was that the higher bond strength allows bonding of larger units, leading to materials with larger porosity.…”

Functional Porous Structures Based on the Pyrolysis of Cured Templates of Block Copolymer and Phenolic Resin

“…[2,[11][12][13][14][15][16][17][18][19][20] These materials can have large void volumes and high internal surface areas, but the supramolecular materials often tend to collapse upon emptying the pores. Several approaches have also been presented to prepare mesoporous and macroporous materials, such as "track-etching", [4][5][6] using honeycomb structures, [27][28][29] and emptying nanostructured templates (e.g., sol-gel processing of surfactants or block copolymers, [7][8][9][10] selective degradation of material with UV exposure, [24][25][26] pyrolysis, [21][22][23]34] and selective removal of lowmolecular-weight amphiphiles (combs) from hierarchically self-assembled polymeric comb-coil supramolecules [35,36] ). Block copolymers provide ideal structures for templates, as, by a facile route, they self-assemble into various structures as a result of the repulsion between the covalently bonded blocks; examples include the spherical, cylindrical, lamellar, and gyroid structures.…”

From molecular modules to modular materials

“…(Fig. 4) [61]. The mesoporous material achieved with this complex shows a lamellar structure, and even points toward a structural hierarchy for high-molecular-weight block copolymer.…”