Design Rationale for CO2 Separation Membranes with Micropatterned Surface Structures

Here, we report the design rationale of CO2 separation membranes with micropatterned surface structures. Thin film composite (TFC) membranes with micropatterned surface structures were fabricated by spray coating amine-containing hydrogel particles on the top of micropatterned porous support membranes, which were synthesized by a polymerization-induced phase separation process in a micromold (PIPsμM). The pore size of the support membranes was optimized by tuning the proportion of good and poor solvents for the polymerization process so that the microgels would be assembled as a defect-free separation layer. The relationship between the size of the micropatterned structures on the surface of the support membrane and the thickness of the separation layer was optimized to maximize the surface area of the separation layer. The rationally designed micropatterned TFC membrane showed a CO2 permeability (835.8 GPU) proportional to the increase in surface area relative to the flat membrane with a high CO2/N2 selectivity of 58.7. The rational design for micropatterned TFC membranes will enable the development of inexpensive and high-performance functional membranes not only for CO2 separation but also for other applications such as water treatment and membrane reactors.

CO2-responsive gels

CO₂-responsive materials undergo a change in chemical or physical properties in response to the introduction or removal of CO₂. The use of CO₂ as a stimulus is advantageous as it is abundant, benign, inexpensive, and it does not accumulate in a system. Many CO₂-responsive materials have already been explored including polymers, latexes, surfactants, and catalysts. As a sub-set of CO₂-responsive polymers, the study of CO₂-responsive gels (insoluble, cross-linked polymers) is a unique discipline due to the unique set of changes in the gels brought about by CO₂ such as swelling or a transformed morphology. In the past 15 years, CO₂-responsive gels and self-assembled gels have been investigated for a variety of emerging potential applications, reported in 90 peer-reviewed publications. The two most widely exploited properties include the control of flow (fluids) via CO₂-triggered aggregation and their capacity for reversible CO₂ absorption-desorption, leading to applications in Enhanced Oil Recovery (EOR) and CO₂ sequestration, respectively. In this paper, we review the preparation, properties, and applications of these CO₂-responsive gels, broadly classified by particle size as nanogels, microgels, aerogels, and macrogels. We have included a section on CO₂-induced self-assembled gels (including poly(ionic liquid) gels).

Effect of Charge Groups Immobilized in Hydrogel Microspheres during the Evaporation of Aqueous Sessile Droplets

In contrast to conventional dispersions of solid microspheres, dilute dispersions containing soft hydrogel microspheres (microgels) exhibit unique drying behavior due to their selective adsorption at the air/water interface of sessile droplets. So far, the impact of the size, chemical composition, and softness (degree of cross-linking) of microgels has been investigated. In the present study, we present the impact of charged groups introduced in the microgels on the adsorption and assembly behavior of these microgels at the air/water interface using a series of microgels with different amounts and distribution of charged groups. A series of experiments under different conditions (pH value and ionic strength) afforded information that clarified the adsorption, interpenetration, and deformation behavior of such charged microgels at the air/water interface. The results indicate that the adsorption and the deformation of charged microgels at the air/water interface are suppressed by the presence of charged groups. Moreover, charged microgels adsorbed at the interface are more dynamic and not highly entangled with each other; i.e., even though the more dynamic charged microgels are arranged at the interface, these arranged structures are disrupted upon transferring onto the solid substrates. Our findings of this study can be expected to promote the further development of applications, e.g., foams and emulsions stabilized by microgels, that crucially requires an in-depth understanding of the adsorption behavior of charged microgels at the air/water interface such as coatings.

The phosphinoboration of carbodiimides, isocyanates, isothiocyanates and CO2

The transition metal-free addition of phosphinoboronate ester Ph₂PBpin (pin = 1,2-O₂C₂Me₄) to heterocumulenes including carbodiimides, isocyanates, isothiocyanates and carbon dioxide proceeds with remarkable selectivity to give products in high yield.