Crystallization-modulated nanoporous polymeric materials with hierarchical patterned surfaces and 3D interpenetrated internal channels

Recent Advancements in Fabrication, Separation, and Purification of Hierarchically Porous Polymer Membranes and Their Applications in Next-Generation Electrochemical Energy Storage Devices

In recent years, hierarchically porous polymer membranes (HPPMs) have emerged as promising materials for a wide range of applications, including filtration, separation, and energy storage. These membranes are distinguished by their multiscale porous structures, comprising macro-, meso-, and micropores. The multiscale structure enables optimizing the fluid dynamics and maximizing the surface areas, thereby improving the membrane performance. Advances in fabrication techniques such as electrospinning, phase separation, and templating have contributed to achieving precise control over pore size and distribution, enabling the creation of membranes with properties tailored to specific uses. In filtration systems, these membranes offer high selectivity and permeability, making them highly effective for the removal of contaminants in environmental and industrial processes. In electrochemical energy storage systems, the porous membrane architecture enhances ion transport and charge storage capabilities, leading to improved performance in batteries and supercapacitors. This review highlights the recent advances in the preparation methods for hierarchically porous structures and their progress in electrochemical energy storage applications. It offers valuable insights and references for future research in this field.

Effect of PMMA Molecular Weight on Its Localization during Crystallization of PVDF in Their Blends

In miscible crystalline/amorphous polymer blends, the exclusion behaviors of the latter with various molecular weights during the crystallization of the former were investigated by the combination of SAXS and DSC by taking a PVDF/PMMA blend as an example. The ratio between internal crystallinity from SAXS and overall crystallinity of the entire blend from DSC was employed to characterize the exclusion of PMMA. Our results indicate that the molecular weight of the amorphous component produces a remarkable influence on the diffusion coefficient (D) and the crystal growth rate (G) of the crystalline component. There are both inter-lamellar and inter-fibrillar structures when PVDF blended with lower-molecular-weight PMMA. With increasing molecular weight of PMMA, the decrease in crystal growth rate (G) dominates the enhanced exclusion behaviors of PMMA, resulting in bigger pores after extraction. Our results are significant not only for the basic understanding of crystallization in polymer blends, but also for the fabrication and structure control of porous structures based on crystallization templates.

Development of Polyoxymethylene/Polylactide Blends for a Potentially Biodegradable Material: Crystallization Kinetics, Lifespan Prediction, and Enzymatic Degradation Behavior

This paper reported the development of polyoxymethylene (POM)/polylactide (PLA) blends for a potentially biodegradable material. A series of POM/PLA blends at different weight ratios were prepared by melt extrusion with a twin-screw extruder, and their mechanical properties, crystallization behavior and kinetics, thermal degradation kinetics and stability, lifespan prediction and enzymatic degradation behavior were investigated extensively. POM and PLA were found to be partially miscible in the melt state at low temperature and become phase-separated at elevated temperatures, and their blends exhibited a typical lower critical solution temperature behavior. There were two distinct glass transition temperatures (Tg) observed for POM/PLA blends at any mass ratios when quenched from the homogeneous state, and both POM and PLA domains showed an apparent depression in their respective Tg's in the blends. Owing to the partial miscibility between two domains, the tensile strength and impact toughness of POM/PLA blends gradually decreased with an increase of PLA content, but their flexural strength and modulus presented an increasing trend with PLA content. The studies on non-isothermal and isothermal crystallization behaviors of the blends indicated that the crystallization rates of the blends decreased continually with increasing the PLA content, confirming that the crystallization of POM domain was controlled by the molecular-confined mechanism. The introduction of PLA into POM not only led to a slight increase of thermal stability of POM domain at low PLA contents but also shortened the lifespan of the blends, favoring the natural degradation of the blends. The POM/PLA blends exhibited an improvement in partially biodegradable performance with an increase of PLA content and their mass loss reached up to 25.3 wt % at the end of 48-h enzymatic degradation when 50 wt % of PLA was incorporated.

Fabrication of Superhydrophobic Surfaces with Controllable Electrical Conductivity and Water Adhesion

A facile and versatile strategy for fabricating superhydrophobic surfaces with controllable electrical conductivity and water adhesion is reported. "Vine-on-fence"-structured and cerebral cortex-like superhydrophobic surfaces are constructed by filtering a suspension of multiwalled carbon nanotubes (MWCNTs), using polyoxymethylene nonwovens as the filter paper. The nonwovens with micro- and nanoporous two-tier structures act as the skeleton, introducing a microscale structure. The MWCNTs act as nanoscale structures, creating hierarchical surface roughness. The surface topography and the electrical conductivity of the superhydrophobic surfaces are controlled by varying the MWCNT loading. The vine-on-fence-structured surfaces exhibit "sticky" superhydrophobicity with high water adhesion. The cerebral cortex-like surfaces exhibit self-cleaning properties with low water adhesion. The as-prepared superhydrophobic surfaces are chemically resistant to acidic and alkaline environments of pH 2-12. They therefore have potential in applications such as droplet-based microreactors and thin-film microextraction. These findings aid our understanding of the role that surface topography plays in the design and fabrication of superhydrophobic surfaces with different water-adhesion properties.

Electrospun nanofibers with both surface nanopores and internal interpenetrated nanochannels for oil absorption

We report novel polyoxymethylene nanofibers with both surface nanopores and internal interpenetrated channels. Their novel interesting structure makes them an ideal alternative for oil adsorption, oil/water separation or catalysis in the future.