Improvement in the CO2 Permeation Properties of High-Molecular-Weight Poly(ethylene oxide): Use of Amine-Branched Poly(amidoamine) Dendrimer

High-Loading Poly(ethylene glycol)-Blended Poly(acrylic acid) Membranes for CO2 Separation

Poly(ethylene glycol) (PEG) is an amorphous material of interest owing to its high CO₂ affinity and potential usage in CO₂ separation applications. However, amorphous PEG often has a low molecular weight, making it challenging to form into the membrane. The crystalline high average molar mass poly(ethylene oxide) (PEO) cannot exhibit CO₂ separation characteristics. Thus, it is crucial to employ low molecular weight PEG in high molecular weight polymers to increase the CO₂ affinity for CO₂ separation membranes. In this work, poly(acrylic acid) (PAA)/PEG blend membranes with a PEG-rich phase were simply fabricated by physical mixing with an ethanol solvent. The carbonyl group of the PAA and the hydroxyl group of the PEG formed a hydrogen bond. Furthermore, the thermal stability, glass transition temperature, and surface hydrophilicity of PAA/PEG blend membranes with various PEG concentrations were further characterized. The PAA/PEG(1:9) blend membrane exhibited an improved CO₂ permeability of 51 Barrer with high selectivities relative to the other gas species (H₂, N₂, and CH₄; CO₂/H₂ = 6, CO₂/N₂ = 63, CO₂/CH₄ = 21) at 35 °C and 150 psi owing to the enhanced CO₂ affinity with the amorphous PEG-rich phase. These PAA/PEG blend membrane permeation characteristics indicate a promising prospect for CO₂ capture applications.

An overview of poly (amide-amine) dendrimers functionalized chromatographic separation materials

Chromatography is one of the most important separation techniques in analytical chemistry. In which, the separation materials are the core for good separation results. Poly (amide-amine) dendrimers with regular three-dimensional structure, abundant terminal groups, controllable molecule chains, and unique cavities appear to have a positive impact on chromatographic separation materials. In the past decades, poly (amide-amine) grafted adsorbents and stationary phases have presented high grafting efficiency, controllable surface structure, good dispersion, and wide practical applications. In this review, the prepared poly (amide-amine) functionalized separation materials and their applications are systematically summarized. Functions, significance, structure-actvity relationships and benefits of poly (amide-amine) dendrimers in the proposed separation materials are discussed in detail. And we hope to provide a useful reference for the future development of chromatographic separation materials and inspire new discoveries in the study of poly (amide-amine) functionalized materials.

Recent Advances in Polymer-Inorganic Mixed Matrix Membranes for CO2 Separation

Since the second industrial revolution, the use of fossil fuels has been powering the advance of human society. However, the surge in carbon dioxide (CO2) emissions has raised unsettling concerns about global warming and its consequences. Membrane separation technologies have emerged as one of the major carbon reduction approaches because they are less energy-intensive and more environmentally friendly compared to other separation techniques. Compared to pure polymeric membranes, mixed matrix membranes (MMMs) that encompass both a polymeric matrix and molecular sieving fillers have received tremendous attention, as they have the potential to combine the advantages of both polymers and molecular sieves, while cancelling out each other's drawbacks. In this review, we will discuss recent advances in the development of MMMs for CO2 separation. We will discuss general mechanisms of CO2 separation in an MMM, and then compare the performances of MMMs that are based on zeolite, MOF, metal oxide nanoparticles and nanocarbons, with an emphasis on the materials' preparation methods and their chemistries. As the field is advancing fast, we will particularly focus on examples from the last 5 years, in order to provide the most up-to-date overview in this area.

Synthesis, Characterization, and CO2/N2 Separation Performance of POEM-g-PAcAm Comb Copolymer Membranes

Alcohol-soluble comb copolymers were synthesized from rubbery poly(oxyethylene methacrylate) (POEM) and glassy polyacrylamide (PAcAm) via economical and facile free-radical polymerization. The synthesis of comb copolymers was confirmed by Fourier-transform infrared and proton nuclear magnetic resonance spectroscopic studies. The bicontinuous microphase-separated morphology and amorphous structure of comb copolymers were confirmed by wide-angle X-ray scattering, differential scanning calorimetry, and transmission electron microscopy. With increasing POEM content in the comb copolymer, both CO₂ permeability and CO₂/N₂ selectivity gradually increased. A mechanically strong free-standing membrane was obtained at a POEM:PAcAm ratio of 70:30 wt%, in which the CO₂ permeability and CO₂/N₂ selectivity reached 261.7 Barrer (1 Barrer = 10⁻¹⁰ cm³ (STP) cm cm⁻² s⁻¹ cmHg⁻¹) and 44, respectively. These values are greater than those of commercially available Pebax and among the highest separation performances reported previously for alcohol-soluble, all-polymeric membranes without porous additives. The high performances were attributed to an effective CO₂-philic pathway for the ethylene oxide group in the rubbery POEM segments and prevention of the N₂ permeability by glassy PAcAm chains.