Multicomponent Nanomaterials with Complex Networked Architectures from Orthogonal Degradation and Binary Metal Backfilling in ABC Triblock Terpolymers

Abstract

Selective degradation of block copolymer templates and backfilling the open mesopores is an effective strategy for the synthesis of nanostructured hybrid and inorganic materials. Incorporation of more than one type of inorganic material in orthogonal ways enables the synthesis of multicomponent nanomaterials with complex yet well-controlled architectures; however, developments in this field have been limited by the availability of appropriate orthogonally degradable block copolymers for use as templates. We report the synthesis and self-assembly into cocontinuous network structures of polyisoprene-block-polystyrene-block-poly(propylene carbonate) where the polyisoprene and poly(propylene carbonate) blocks can be orthogonally removed from the polymer film. Through sequential block etching and backfilling the resulting mesopores with different metals, we demonstrate first steps toward the preparation of three-component polymer-inorganic hybrid materials with two distinct metal networks. Multiblock copolymers in which two blocks can be degraded and backfilled independently of each other, without interference from the other, may be used in a wide range of applications requiring periodically ordered complex multicomponent nanoarchitectures.

Figure 1

Synthesis and orthogonal degradation schemes of ABC triblock terpolymer PI-b-PS-b-PPC. (a) Synthesis of PI-b-PS-OH using anionic polymerization and synthesis of PI-b-PS-b-PPC triblock terpolymers from the parent PI-b-PS-OH diblock copolymer using rapid chain-shuttling polymerization of propylene oxide and CO₂ using 1. (b) Schematic illustrating orthogonal degradation of PI and PPC blocks of PI-b-PS-b-PPC from a Q²³⁰ core–shell double gyroid structure using 302 nm UV light and NaOH.

Figure 2

Orthogonal degradation of PI-b-PS-b-PPC polymer films (Q²³⁰ and O⁷⁰) as evidenced by GPC. (a,b) GPC traces of PI-b-PS-b-PPC-1 polymer films after (a) degradation of the PI (matrix) blocks followed by degradation of the PPC (gyroid minority networks) blocks; (b) degradation of the PPC blocks followed by degradation of the PI blocks.

Figure 3

Orthogonal degradation of PI-b-PS-b-PPC polymer films (Q²³⁰ and O⁷⁰) as evidenced by SEM micrographs of the corresponding polymer film cross sections after (a) degradation of PI blocks only (PI-b-PS-b-PPC-3); (b) degradation of PPC blocks only (PI-b-PS-b-PPC-3); (c) degradation of PI blocks followed by degradation of PPC blocks (PI-b-PS-b-PPC-1); (d) degradation of PPC blocks followed by degradation of the PI blocks (PI-b-PS-b-PPC-1).

Figure 4

TEM micrographs of metal deposited into networked porous templates using electroless deposition (Cu, Ni), and seeded growth deposition (Au). Scale bars indicate 250 nm; inset scale bars indicate 50 nm. (a) Deposition of Au in PI pores (PI-b-PS-b-PPC-4) and (b) PPC pores (PI-b-PS-b-PPC-3). (c) Deposition of Ni metal into PI pores (PI-b-PS-b-PPC-4) and (d) PPC pores (PI-b-PS-b-PPC-1). (e) Deposition of Cu metal into matrix PI pores (PI-b-PS-b-PPC-4) and (f) minority network in PI pores (PI-b-PS-b-PPC-2).

Figure 5

Orthogonal deposition of Au and Cu metal into PI-b-PS-b-PPC-4 triblock terpolymer templates. (a) TEM micrograph of Au and Cu metal networks; dark regions indicate the presence of metal. (b) SEM micrograph (secondary electron detector) of Au and Cu metal networks; PS block was removed using dissolution in THF.

Figure 6

HAADF STEM micrographs of Au and Cu metal networks from PI-b-PS-b-PPC-4 terpolymer templates. (a,b) HAADF STEM micrographs of Au and Cu networks in single template; bright regions indicate Au metal, while gray regions indicate Cu metal. Black regions indicate vacuum or organic material. (c–f) Incoherent STEM simulations of Q²³⁰ double gyroid metal structures. Metal networks appear bright while organic domains remain dark. (c,e) Simulations of projections in (a,b) with Au metal only in the matrix (majority) network pores. (d,f) Simulations of projections in (a,b) with Cu metal in both majority network and minority network pores.

Figure 7

3D reconstruction of Au and Cu metal networks from PI-b-PS-b-PPC-4 terpolymer templates. (a,b) 3D reconstruction with HAADF STEM tomography of Au (yellow isosurface rendering) and Cu (red volume rendering) metal networks where red regions indicate Cu metal and yellow regions indicate Au metal. (a) Large-area reconstructed region and (b) close up of region contained in white box in (a) revealing both Cu and Au networks.