Morphology Control in Mesoporous Carbon Films Using Solvent Vapor Annealing

Abstract

Ordered mesoporous (2-50 nm) carbon films were fabricated using cooperative self-assembly of a phenolic resin oligomer with a novel block copolymer template (poly(styrene-block-N,N-dimethyl-n-octadecylamine p-styrenesulfonate), (PS-b-PSS-DMODA)) synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Due to the high Tg of the PS segment and the strong interactions between the phenolic resin and the PSS-DMODA, the segmental rearrangement is kinetically hindered relative to the cross-linking rate of the phenolic resin, which inhibits long-range ordering and yields a poorly ordered mesoporous carbon with a broad pore size distribution. However, relatively short exposure (2 h) to controlled vapor pressures of methyl ethyl ketone (MEK) yields significant improvements in the long-range ordering and narrows the pore size distribution. The average pore size increases as the solvent vapor pressure during annealing increases, but an upper limit of p/p0 = 0.85 exists above which the films dewet rapidly during solvent vapor annealing. This approach can be extended using mesityl oxide, which has similar solvent qualities to MEK, but is not easily removed by ambient air drying after solvent annealing. This residual solvent can impact the morphology that develops during cross-linking of the films. These results illustrate the ability to fine-tune the mesostructure of ordered mesoporous carbon films through simple changes in the processing without any compositional changes in the initial cast film.

Highly aligned, large pore ordered mesoporous carbon films by solvent vapor annealing with soft shear

“…The porosity of non-SVA film is approximately 23% and the porosity increases to 27% when SVA is applied. This increase is attributed to improvements in to the ordered structure that decrease the film contraction during the carbonization, which is consistent with the previous results [31]. However, there is no significant difference in the porosity between the mesoporous carbon films annealed by SVA and SVA-SS (28%).…”

“…This dynamic nature of the mesostructure in films provides opportunities for improved control of the ordered structure, but the thermal energy that enables ordering of the nanostructure also drives the crosslinking of the resol precursor. This leads to a competition between the crosslinking and ordering kinetics that can limit the quality of the ordered structures [31].…”

“…The initial report of soft-templated ordered mesoporous carbon used solvent vapor annealing (SVA) to produce the highly ordered mesostructure, which likely drove orientation of the cylindrical mesopores through the thickness of the film [32]. We have recently illustrated that the kinetic frustrations with ordering from the cooperative assembly of resol with a high molecular block copolymer template can be overcome by an analogous SVA process [31,33]. However, these self-assembled mesostructures lack registration over macroscopic dimensions with randomly oriented ordered grains.…”

Self‐Healing Actuating Adhesive Based on Polyelectrolyte Multilayers

“…The cell geometry dictated the angle of incidence to be 75°, and a limited wavelength range from 300 to 1150 nm was applied for the recursive fits due to the absorption of solvents in the ultraviolet and near‐infrared light region. Standard window correction protocols with a silicon wafer with thermal oxide (25.0 nm) as the reference were used before each measurement . The ellipsometry data were fitted by applying a four‐layer model consisting of a silicon substrate layer, a fixed 1.0 nm Si–SiO 2 interface layer, a 0.8 nm thermal oxide layer, and a Cauchy layer (with thickness, A and B free fit parameters) in Complete EASE (J.…”

Facile non‐lithographic route to highly aligned silica nanopatterns using unidirectionally aligned polystyrene‐block‐polydimethylsiloxane films

“…Sufficient time was allowed for the PDMS to fully wet the BCP films prior to the SVA (∼1 min). Mass flow controllers (MKS‐146C‐FF000–1) were used to control the flow rate of solvent vapor and dry air as previously reported . To align the nanostructure, the BCP films were first annealed by nearly saturated THF solvent vapor at 800 mL/min for 3 h and subsequently dried by flowing dry air at 250 mL/min for 20 min.…”