Effect of the Micelle Opening in Self-assembled Amphiphilic Block Co-polymer Films on the Infiltration of Inorganic Precursors

Abstract

Infiltration of the polymer templates with inorganic precursors using the selective vapor-phase infiltration approach, or sequential infiltration synthesis (SIS), allows the design of materials with advanced properties. Swelling of the block co-polymer (BCP) templates enables the additional control of the structure, porosity, and thickness of the composite or inorganic materials. Here, we use the highly precise quartz crystal microbalance (QCM) technique to investigate quantitatively the effect of the micelle opening by swelling and inorganic precursor infiltrating on the evolution of porosity in amphiphilic BCPs. We show that swelling of the polystyrene-block-poly-4-vinyl pyridine (PS-b-P4VP) BCP in ethanol at 75 °C occurs rapidly and results in a stable polymer structure in 30 min. By using an alumina model system, we found that swelling enables access to all available polar domains of the PS-b-P4VP film leading to an increase in the SIS-infiltrated alumina mass as compared to the nonswelled BCP layer. Our results demonstrate that swelling of the 110 nm thick BCP template results in the formation of 192 nm thick alumina films with 2 times larger alumina mass and 4 times larger effective pore volume than in case of the nonswelled sample. In the case of the thicker polymer template, the difference due to swelling becomes even more substantial because the fraction of accessible polymer is increased much more than in thin films. Our findings provide important insights into the mechanism of the infiltration of the inorganic precursors into swelled and nonswelled, spin-coated BCP templates enabling the design of highly porous thick ceramic films by SIS.

Resolving Triblock Terpolymer Morphologies by Vapor-Phase Infiltration

“…We assume that the low volume fraction of the PLA limited the infiltration of Zn into the cylinder cores, which were not resolved in Figure S6. We note that self-assembled BCP films in general can be swelled when exposed to infiltrating precursors as organic vapors can do, but our TEM data clearly indicate no disruption of the self-assembled BCP morphology by the precursor infiltration. This is most likely due to the purging step included in the infiltration protocol, which removes the unreacted precursor out of the BCP film.…”

Block-Co-polymer-Assisted Synthesis of All Inorganic Highly Porous Heterostructures with Highly Accessible Thermally Stable Functional Centers

“…Sequential infiltration synthesis (SIS) has been developed to pattern metal oxides materials via selective infiltration of the polar domains of the block-co-polymer (BCP) templates with inorganic vapors followed by removal of the polymer using thermal annealing. , SIS has been successfully used to pattern ceramic structures such as alumina, titanium oxide, zinc oxide, and silicon oxide. − However, the thickness of coatings obtained by classical SIS is limited by the depth of diffusion of inorganic vapor-phase precursors into a polymer template. For standard BCP templates, such as poly­(methyl methacrylate)/polystyrene (PMMA/PS) and poly­(vinyl pyridine)/polystyrene (PVP/PS), this infiltration depth value is ∼40 nm. , The swelling of the BCP template in a polar solvent (e.g., ethanol) increases the possible infiltration depth significantly through the introduction of additional porosity channels . Quartz crystal microbalance (QCM) studies confirmed high interconnectivity of the resulting pores in inorganic structures prepared via swelling-assisted SIS .…”

“…For standard BCP templates, such as poly­(methyl methacrylate)/polystyrene (PMMA/PS) and poly­(vinyl pyridine)/polystyrene (PVP/PS), this infiltration depth value is ∼40 nm. , The swelling of the BCP template in a polar solvent (e.g., ethanol) increases the possible infiltration depth significantly through the introduction of additional porosity channels . Quartz crystal microbalance (QCM) studies confirmed high interconnectivity of the resulting pores in inorganic structures prepared via swelling-assisted SIS . Swelling-based modification of the SIS approach enabled its use for the design of single-layer and multilayered antireflective alumina coatings on glass with reduced Fresnel reflection down to 0.1% over a broad spectral range .…”

Swelling-Assisted Sequential Infiltration Synthesis of Nanoporous ZnO Films with Highly Accessible Pores and Their Sensing Potential for Ethanol

“…30 Our previous studies demonstrated improved infiltration of the BCP after the selective swelling in ethanol as a result of the increased number of reactive infiltration sites, thus suggesting the importance of the swelling step prior to the SIS. 31,32 In addition, the swelling increases the porosity, enabling the synthesis of high-surface-area films. 32 As in the case of alumina, we also observed that swelling of the BCP template allowed a significant increase in the infiltration efficiency of the BCP with ZnO precursors.…”

“…31,32 In addition, the swelling increases the porosity, enabling the synthesis of high-surface-area films. 32 As in the case of alumina, we also observed that swelling of the BCP template allowed a significant increase in the infiltration efficiency of the BCP with ZnO precursors. In this study, we explored the swelling of the BCPs with a different contribution of polar domains such as PS25-b-P4VP25 and PS75-b-P4VP25.…”