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Ion-conducting polymers (Ionomers) are critical in catalyst layers (CLs) of proton exchange membrane (PEM) fuel cells and water/vapor-fed electrolyzers, serving essential roles in proton conduction, electronic insulation, and water absorption. This review summarized the physical, chemical and economic parameters of CL ionomers across various PEM modules, focusing on long- and short-side-chain perfluorosulfonic acid (PFSA) ionomers. It also outlines recent efforts in PEM air dehumidification. Characterization methods for ionomer morphology (e.g. rods, swollen clusters, networks) and mass transfer resistance (e.g. ionomer/gas interfacial, catalyst/ionomer interfacial and intra-ionomer) were summarized. Optimal ionomer distribution at electron-proton-gas interfaces is crucial, as proton transfer requiring a thick and connected distribution and gas transport requiring a thin and dispersed distribution. Adjusting ionomer equivalent weight and ratio to catalyst can enhance distribution. Besides, CL ionomer design should emphasize product escape for water electrolyzers and reactant diffusion for vapor ones. Integration of multidimensional and multifunctional techniques, such as visual characterizations of Transmission Electron Microscopy and Nanoscale X-ray computed tomography and numerical simulations of Molecular Dynamics and lattice Boltzmann methods, is recommended for accurate assessment of ionomer behavior. This comprehensive review provides insights into ionomers in CLs, highlighting characterization methods and manipulation strategies, offering guidance for next-generation PEM modules. [ABSTRACT FROM AUTHOR]

Visible light responsive micellar drug delivery formulations are of notable interest for the treatment of ocular diseases, as their successful development would enable controlled drug release at the back of the eye, improving efficacy and reducing side-effects when compared to existing approaches. In this work, an aliphatic polycarbonate-based visible light responsive micelle formulation based on mPEG-b-poly(5-hydroxy-trimethylene carbonate) (PHTMC) was prepared wherein the pendant hydroxyl groups of the PHTMC repeating units were protected by blue light-labile [7-(diethylamino)coumarin-4-yl]methyl (DEACM). The photo-labile DEACM provided a photo-triggered release profile, as, upon the removal of these protecting groups by photo-irradiation, the micelles underwent structural disruption, leading to the release of the payload. The removal of DEACM also deprotected the pendant hydroxyl groups of PHTMC, leading to PHTMC backbone degradation via intramolecular cyclization. [ABSTRACT FROM AUTHOR]

Proper catalyst coated membrane (CCM) methods are significant for membrane electrode assembly (MEA) of PEM-based electrolytic dehumidification. In this work, four CCM processes, doctor blade, decal, electrostatic spraying, and modified pneumatic spraying methods, were employed for fabricating dehumidifier assemblies with low-load (0.6 mg/cm2) IrO2 catalyst layers (CLs). The physical and electrochemical properties of the as-prepared CLs were characterized, and the mass transfer resistance and dehumidification rate of the MEA were tested during actual operations. The optimal hot-pressing parameters were also determined. Results showed that the modified pneumatic spraying method can significantly improve the pore distribution and CL flatness by promoting the evaporation of solvent from catalyst slurry. The charge-transfer and ohmic resistances of MEA was 25.3 and 27.8 mΩ/cm2, respectively, which are the best values for those prepared using the four methods. The dehumidification rate was also the highest (0.105 g/h), 20–40% higher than that of other methods. Although the overall mass transfer resistance of assembly prepared by the electrostatic spraying was low, the CL structure was obviously loose and unable to bind to the membrane surface tightly, leading to high electrochemical resistance (6.6-fold that of pneumatic spray method). Besides, catalyst particles tend to agglomerate using the doctor blade method. The pore size of the CL prepared using the decal method was found to be too small (<300 nm), hindering reactant transfer and resulting in a low overall mass transfer coefficient. This study provides a practical direction for the preparation of economical and high-performance dehumidifiers or electrolyzers. [ABSTRACT FROM AUTHOR]