The induction of macro and mesopores into two-dimensional porous covalent organic frameworks (COFs) could enhance the exposure of the intrinsic micropores toward the pollutant environment, thereby, improving the performance. However, the challenge is to build a continuous hierarchically porous macro-architecture of crystalline organic materials in the bulk scale. In this regard, we have strategized a novel synthetic method to create hierarchically porous COF foams consisting of ordered micropores (2-2.2 nm), disordered meso and macropores (50 nm to 200 µm) as well as ordered macropores (1.5 mm to 2 cm). Herein, graphene oxide was used for creating disordered macro and meso pores in COF-GO foams. Considering the rheological features of the precursor hydrogel, we could integrate crystalline and porous COF-GO foams into self-supported 3D-printed objects with the desired shapes and sizes. Therefore, we have engineered the 3D macro-architecture of COF-GO foams into complex geometries keeping their structural order and continuous porosity intact over a range of more than a million (10 -9 m to 10 -3 m). The interconnected 3D openings in these COF-GO foams further enhance the rapid and efficient uptake of organic and inorganic pollutants from water (>95% removal within 30 s). The abundant distribution of interconnected macroporous volume (55%) throughout the COF-GO foam matrix enhances the flow of water (1.13 × 10 -3 m.s −1 ) which results in efficient mass transport and adsorption.

Liquid−air interfaces can be deformed by surfacetension gradients to create topography, a phenomenon useful for polymer film patterning. A recently developed method creates these gradients by photochemically patterning a solid polymer film. Heating the film to the liquid state leads to flow driven by the patterned surface-tension gradients, but capillary leveling and diffusion of surface-active species facilitate eventual dissipation of the topography. However, experiments demonstrate that using blends of high-and low-molar-mass polymers can considerably delay the decay in topography. To gain insight into this observation, we develop a model based on lubrication theory that yields coupled nonlinear partial differential equations describing how the film height and species concentrations evolve with time and space. Incorporation of a nonmonotonic disjoining pressure is found to significantly increase the lifetime of topographical features, making the model predictions qualitatively consistent with experiments. A parametric study reveals the key variables controlling the kinetics of film deformation and provides guidelines for photochemically induced Marangoni patterning of polymer films.

Melt blowing is a widely used process for manufacturing nonwoven fiber products with applications spanning healthcare, agriculture, transportation, and infrastructure, among others. The process includes extrusion of a polymer melt through orifices, drawing fiber using high-speed air jets, solidification by cooling with entrained ambient air, and collection in the form of a fiber mat. The structural features and properties of the final mat are determined by a complex interplay between materials selection and fiber dynamics, air flow, and temperature characteristics from die to collector. For the latter, both process variable values and geometrical factors have substantial influence. Many experimental investigations have advanced fundamental understanding in this area, but these studies are challenging due to high air velocities, high temperatures, and the often space-constrained nature of the process, especially near the die exit. Such complexities have sparked significant interest in developing mathematical models and using computer simulations to reveal deeper fundamental insights. Herein, we review advances in melt blowing simulations by presenting employed methods and key findings in the area. We finish by describing some challenges and opportunities for further research.

No abstract

It is of immense interest to exert spatial and temporal control of chemical reactions.I ti sn ow demonstrated that irradiation can trigger reactions specifically at the surface of as imple colloidal construct, obtained by adsorbing polyethyleneimine on fluorescent colloidal particles.E xciting the fluorescent dye in the colloid affords photoinduced electron transfer to spatially proximala mine groups on the adsorbed polymer to form free radical ions.Itisdemonstrated that these can be harnessed to polymerize acrylic acid monomer at the particle surface,ortobreak up colloidal assemblies by cleaving across-linked polymer mesh. Formation of free radical ions is not afunction of the size of the colloid, neither is it restricted to aspecific fluorophore.Fluorophores with redoxpotentials that allowphotoinduced electron transfer with amine groups show formation of free radical ions.