Ordered Nanoporous Carbons with Broadly Tunable Pore Size Using Bottlebrush Block Copolymer Templates

Abstract

We report the preparation of ordered porous carbon materials with tailored pore sizes selected between 16 and 108 nm using bottlebrush block copolymers (BBCPs) as templates. The nanoporous carbons are prepared via the cooperative assembly of polydimethylsiloxane-block-poly(ethylene oxide) (PDMS-b-PEO) BBCPs with phenol−formaldehyde resin yielding ordered precursor films, followed by carbonization. The assembly of PDMS-b-PEO BBCPs with the resin leads to films exhibiting a spherical morphology (PDMS as the minor domain) with uniform domain sizes between 18 and 150 nm in the bulk. The assembled PDMS sphere diameters scale linearly with BBCPs molecular weights, allowing precise control of domain size. Access to very large ordered domains is an enabling hallmark of BBCPs self-assembly, but reports of well-ordered spherical domains are not common. Carbonization of the ordered precursor films yields nanoporous carbon with uniform and tunable pore size. These nanoporous carbons are shown to exhibit excellent performance as supercapacitor electrodes with capacitance reaching up to 254 F g −1 at a current density of 2 A g −1 .

Strategies for Pore-Diameter Control in Mesoporous Carbons Derived from Organic Self-Assembly Processes

“…Using a more unusual approach, Watkins and co-workers employed bottlebrush block copolymers to access a wide range of pore diameters, exceeding the mesopore domain (18-150 nm). 69 Thus, under sequential application of norbornene-capped poly(dimethylsiloxane) (PDMS, 4.8 kg/mol) and norbornenecapped PEO (5.0 kg/mol), ring-opening metathesis polymerization (ROMP, Grubbs-type catalysts) delivered the desired block copolymers, whereby a series of compounds with constant mass fractions (50:50, PDMS:PEO) but increasing molar masses was prepared. Thus, the corresponding PDMS-b-PEO bottlebrush copolymers with a very high Mn = 210, 250, 394, 640 and 1800 kg/mol were applied for structure-direction in combination with resol as carbon precursor.…”

Tailored porous carbons enabled by persistent micelles with glassy cores

“…27 A wide range of nanoscale porous carbons have been prepared using these and similar polymers to yield pore sizes ranging from 3.8 to 108 nm. 28,29 Many custom block polymers are not directly soluble in alcohols and are thus processed from THF or other good solvents for both the polymer blocks and the carbon precursors. While convenient, this class of good-solvent approaches generally leads to dynamic micelles that change size in response to the specific solution conditions.…”

“…32,[34][35][36][37][38] These are natural limitations of equilibration-based synthesis approaches where all aspects of the architecture are determined through free-energy minimization. While recent porous carbon reports have added diversity to carbon precursor chemistry, 4,7,39,40 block polymer chemistries, 29,41 feature sizes, 29,[42][43][44] and morphologies, 43,45 none yet Persistent micelle templates (PMTs) are uniquely based upon kinetically controlled micelles which enable the production of porous material series with constant pore size and varied wall thickness. The suppression of chain exchange mechanisms are needed to preserve constant micelle template diameter with an invariant micelle aggregation number.…”

Flexible heteroatom‐doped porous carbon nanofiber cages for electrode scaffolds

“…1,2 Among these materials, porous carbon nanofibers (PCNFs) have attracted intensive studies owing to their virtues of plentiful pore structures and ability of forming flexible scaffolds. [3][4][5] Extensive studies have been developed to fabricate PCNFs, but it is difficult to control their porosity and flexibility simultaneously since mechanical strength is generally inversely proportional to pore volumes. To ensure structural integrity, most PCNFs only contain meso-and micropores with low pore volumes, which greatly limited the performance of PCNFs as scaffold materials.…”

“…In the past few decades, porous nanostructured carbon materials, including activated carbon, carbon nanofibers (CNFs), carbon nanotubes (CNTs) and graphene have received great attention for energy storage devices due to their large specific surface areas (SSAs), low density, and high chemical stability 1,2 . Among these materials, porous carbon nanofibers (PCNFs) have attracted intensive studies owing to their virtues of plentiful pore structures and ability of forming flexible scaffolds 3‐5 . Extensive studies have been developed to fabricate PCNFs, but it is difficult to control their porosity and flexibility simultaneously since mechanical strength is generally inversely proportional to pore volumes.…”