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1. Vapor-Phase-Infiltrated AlO x /PIM-1 “Hybrid Scaffolds” as Solution-Processable Amine Supports for CO 2 Adsorption

   https://doi.org/10.1021/acsapm.1c00452  

   Zhang, Fengyi ; McGuinness, Emily K. ; Ma, Yao ; Ren, Yi ; Leisen, Johannes E. ; Losego, Mark D. ; Lively, Ryan P. ( January 2021 , ACS Applied Polymer Materials)

   null (Ed.)

   Energy-efficient adsorptive CO2 capture requires both adsorbent materials with high CO2 capacity and structured adsorption contactors possessing fast mass transfer kinetics and low pressure drop. The state-of-the-art research primarily focuses on “hard” adsorbents such as mesoporous zeolites and metal–organic frameworks, which exhibit high CO2 capacities but are challenging to translate into structured contactors. Polymer of intrinsic microporosity 1 (PIM-1), a solution-processable microporous polymer, is a “softer” alternative that can be easily fabricated into structured adsorption contactors. In prior research, PIM-1 has been utilized as a “molecular basket” for poly(ethylene imine) (PEI). Despite nanoscale amine dispersion and excellent processability, PEI/PIM-1 composites possess an unstable micropore structure, which collapses at high PEI loadings (∼30%) and results in lower CO2 adsorption capacity than PEI-loaded hard oxides. Here, we applied a post-fabrication polymer stabilization method, vapor phase infiltration (VPI), to improve the CO2 capacity of the PEI/PIM-1 composite without sacrificing its processibility. PIM-1 is fabricated into structured adsorption contactors and then reinforced with amorphous aluminum oxyhydroxide (AlOx) nanostrands via VPI. The resulting AlOx/PIM-1 is a stable, hierarchically porous support, which can be loaded with 40% PEI without pore collapse. Owing to the combination of processibility, comparable CO2 capacity, and high amine efficiency, PEI/AlOx/PIM-1 composites are a promising alternative to PEI-loaded mesoporous oxides. 

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2. Vapor phase infiltration of zinc oxide into thin films of cis -polyisoprene rubber

   https://doi.org/10.1039/D0MA00304B  

   Pilz, Julian ; Coclite, Anna Maria ; Losego, Mark D. ( January 2020 , Materials Advances)

   Elastomers are an important class of polymers for many applications. Often, additives are added to the polymer matrix of elastomers to promote vulcanization or enhance physical or chemical properties. In this study, vapor phase infiltration (VPI) is investigated for transforming unvulcanized cis -polyisoprene (from natural rubber) into an organic/inorganic hybrid material. Specifically, we examine single-cycle infiltration with diethylzinc (DEZ) and water to form infiltrated zinc oxide species. Interestingly, low-temperature pre-heating of the cis -polyisoprene acutely affects the processes of infiltration, including diffusivity, maximum solubility, and chemical reactivity. We attribute these effects to a combination of film relaxation and oxidation. Independent of thermal pre-treatments, all infiltration processes exhibited consistent zinc oxide loading irrespective of purge time between the DEZ and water doses, indicating the presence of a strongly bound intermediate state between the DEZ precursor and the cis -polyisoprene polymer. Increasing infiltration process temperature accelerates diffusion and lowers the maximum solubility, in accordance with Fick's law and gas phase sorption equilibrium. Resulting organic–inorganic hybrid films show enhanced resistance to dissolution in toluene, a good solvent for the pure polymer. 

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3. Toposelective vapor deposition of hybrid and inorganic materials inside nanocavities by polymeric templating and vapor phase infiltration

   https://doi.org/10.1039/D2NA00291D  

   Lovikka, Ville A. ; Airola, Konsta ; McGuinness, Emily ; Zhang, Chao ; Vehkamäki, Marko ; Kemell, Marianna ; Losego, Mark ; Ritala, Mikko ; Leskelä, Markku ( January 2022 , Nanoscale Advances)

   Selective deposition of hybrid and inorganic materials inside nanostructures could enable major nanotechnological advances. However, inserting ready-made composites inside nanocavities may be difficult, and therefore, stepwise approaches are needed. In this paper, a poly(ethyl acrylate) template is grown selectively inside cavities via condensation-controlled toposelective vapor deposition, and the polymer is then hybridized by alumina, titania, or zinc oxide. The hybridization is carried out by infiltrating the polymer with a vapor-phase metalorganic precursor and water vapor either via a short-pulse (atomic layer deposition, ALD) or a long-pulse (vapor phase infiltration, VPI) sequence. When the polymer-MO x hybrid material is calcined at 450 °C in air, an inorganic phase is left as the residue. Various suspected confinement effects are discussed. The infiltration of inorganic materials is reduced in deeper layers of the cavity-grown polymer and is dependent on the cavity geometry. The structure of the inorganic deposition after calcination varies from scattered particles and their aggregates to cavity-capping films or cavity-filling low-density porous deposition, and the inorganic deposition is often anisotropically cracked. A large part of the infiltration is achieved already during the short-pulse experiments with a commercial ALD reactor. Furthermore, the infiltrated polymer is more resistant to dissolution in acetone whereas the inorganic component can still be heavily affected by phosphoric acid. 

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4. Interpreting inorganic compositional depth profiles to understand the rate-limiting step in vapor phase infiltration processes

   https://doi.org/10.1039/D3CP01517C  

   Balogun, Shuaib A. ; Ren, Yi ; Lively, Ryan P. ; Losego, Mark D. ( May 2023 , Physical Chemistry Chemical Physics)

   Vapor phase infiltration (VPI) is a post-polymerization modification technique that infuses inorganics into polymers to create organic–inorganic hybrid materials with new properties. Much is yet to be understood about the chemical kinetics underlying the VPI process. The aim of this study is to create a greater understanding of the process kinetics that govern the infiltration of trimethyl aluminum (TMA) and TiCl 4 into PMMA to form inorganic-PMMA hybrid materials. To gain insight, this paper initially examines the predicted results for the spatiotemporal concentrations of inorganics computed from a recently posited reaction–diffusion model for VPI. This model provides insight on how the Damköhler number (reaction versus diffusion rates) and non-Fickian diffusional processes (hindering) that result from the material transforming from a polymer to a hybrid can affect the evolution of inorganic concentration depth profiles with time. Subsequently, experimental XPS depth profiles are collected for TMA and TiCl 4 infiltrated PMMA films at 90 °C and 135 °C. The functional behavior of these depth profiles at varying infiltration times are qualitatively compared to various computed predictions and conclusions are drawn about the mechanisms of each of these processes. TMA infiltration into PMMA appears to transition from a diffusion-limited process at low temperatures (90 °C) to a reaction-limited process at high temperatures (135 °C) for the film thicknesses investigated here (200 nm). While TMA appears to fully infiltrate these 200 nm PMMA films within a few hours, TiCl 4 infiltration into PMMA is considerably slower, with full saturation not occurring even after 2 days of precursor exposure. Infiltration at 90 °C is so slow that no clear conclusions about mechanism can be drawn; however, at 135 °C, the TiCl 4 infiltration into PMMA is clearly a reaction-limited process, with TiCl 4 permeating the entire thickness (at low concentrations) within only a few minutes, but inorganic loading continuously increasing in a uniform manner over a course of 2 days. Near-surface deviations from the uniform-loading expected for a reaction-limited process also suggest that diffusional hindering is high for TiCl 4 infiltration into PMMA. These results demonstrate a new, ex situ analysis approach for investigating the rate-limiting process mechanisms for vapor phase infiltration. 

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5. Ultrasound-Mediated Nonequilibrium Separation of Ethanol-Water Solutions, Including Avoidance of the Azeotropic Bottleneck

   Kahraman, Ozan ; Pearlstein, Arne ; Feng, Hao ( July 2018 , 2018 AIChE Annual Meeting. AIChE)

   AIChE (Ed.)

   Separation of liquid mixtures, frequently by distillation, is ubiquitous in the chemical and process industries (CPI). Distillation accounts for ~95% of the energy used in liquid separations, ~25–40% of overall energy used in CPI, and ~3% of global energy consumption.1-2 The low efficiency of distillation is largely due to two issues. First, there are large irreversible losses due to heat transfer.3 Second, a significant fraction of energy used in liquid separations is used to separate azeotropic mixtures in azeotrope-forming systems (e.g., ethanol/water). While a number of conventional distillation technologies4-5 (e.g., pressure-swing, extractive distillation, and azeotropic distillation6) and new separation approaches5 (e.g., dividing-wall columns, membranes, molecular sieves, and bio-absorbance) have been developed for azeotropic systems, these approaches largely rely on thermal separation via phase equilibrium or involve large capital and/or operational costs. 

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