Investigation of Roughness Correlation in Polymer Brushes via X-ray Scattering

Polymer Encapsulated Framework Materials for Enhanced Gas Storage and Separations

Within the broader field of energy storage, polymer-encapsulated framework (PEF) materials have witnessed remarkable growth in recent years, with transformative implications for diverse applications. This comprehensive review discusses in detail the latest advancements in the design, synthesis, and applications of PEFs in gas storage and separations. Following a thorough survey of existing literature, the article delves into mechanistic considerations and foundational principles governing PEF synthesis. Emphasis is placed on covalent and coordinative covalent grafting methods, physical blending, nonsolvent utilization, and various vapor deposition techniques. The discussion critically evaluates the advantages and disadvantages of these synthesis approaches, considering factors such as grafting density, coating thickness, and other physical properties relevant to processability and stability in comparison to traditional framework materials. Special attention is given to the impact of polymer coatings on gas adsorption analysis. Finally, notable accomplishments and advancements in the PEF field, including mixed matrix membrane (MMM) technology, improvements in framework form factors, and enhanced chemical and mechanical stability are summarized. This review concludes by offering valuable perspective for researchers, highlighting gaps and challenges that confront the current state-of-the-art in PEF materials, paving the way for future innovations that are poised to help address global energy challenges.

Impact of Grafting Density on the Assembly and Mechanical Properties of Self-Assembled Metal-Organic Framework Monolayers

Polymer-grafted metal-organic frameworks (MOFs) can be used to form free-standing self-assembled MOF monolayers (SAMMs). Polymer chains can be introduced onto MOF surfaces through either the ligands or metal nodes using both grafting-to and grafting-from approaches. However, controlling the grafting density of polymer-grafted MOFs has not yet been achieved, because a means to control the density of grafting sites on the MOF surface has not been developed. In this study, the grafting density of polymer-grafted UiO-66 (UiO = University of Oslo) was controlled by functionalizing a portion of the Zr(IV) secondary building units (SBUs) on a UiO-66 surface with a so-called blocking agent. The remaining sites on the UiO-66 SBUs were functionalized with polymerization initiation groups, and polymers were grown from these sites to obtain particles with variable grafting densities and chain lengths that form SAMMs at an air-water interface. Even under conditions of low grafting density, these materials retain the ability to form SAMMs and their free-standing ability. Changes in particle arrangement within the monolayers were investigated using SEM imaging, and the toughness of the monolayers was evaluated using a film-on-water (FOW) method. Furthermore, coarse-grained molecular dynamics simulations were carried out to elucidate the morphology and mechanical properties of the monolayers. Findings from both experiments and simulations indicate that the toughness of SAMMs is more heavily influenced by the chain length of the grafted polymers than by the overall polymer content in the composite.

Surface functionalization of a chalcogenide IR photonic sensor by means of a polymer membrane for water pollution remediation

Rapid, simultaneous detection of organic chemical pollutants in water is an important issue to solve for protecting human health. This study investigated the possibility of developing an in situ reusable optical sensor capable of selective measurements utilizing a chalcogenide transducer supplemented by a hydrophobic polymer membrane with detection based on evanescent waves in the mid-infrared spectrum. In order to optimise a polyisobutylene hydrophobic film deposited on a chalcogenide waveguide, a zinc selenide prism was utilized as a testbed for performing attenuated total reflection with Fourier-transform infrared spectroscopy. To comply with the levels mentioned in health guidelines, the target detection range in this study was kept rather low, with the concentration range extended from 50 ppb to 100 ppm to cover accidental pollution problems, while targeted hydrocarbons (benzene, toluene, and xylene) were still detected at a concentration of 100 ppb. Infrared measurements in the selected range showed a linear behaviour, with the exception of two constantly reproducible plateau phases around 25 and 80 ppm, which were observable for two polymer film thicknesses of 5 and 10 μm. The polymer was also found to be reusable by regenerating it with water between individual measurements by increasing the water temperature and flow to facilitate reverse exchange kinetics. Given the good conformability of the hydrophobic polymer when coated on chalcogenide photonic circuits and its demonstrated ability to detect organic pollutants in water and to be regenerated afterwards, a microfluidic channel utilising water flow over an evanescent wave optical transducer based on a chalcogenide waveguide and a polyisobutylene (PIB) hydrophobic layer deposited on its surface was successfully fabricated from polydimethylsiloxane by filling a mold prepared via CAD and 3D printing techniques.

Antibacterial Zirconia Surfaces from Organocatalyzed Atom-Transfer Radical Polymerization

Antibacterial coatings are becoming increasingly attractive for application in the field of biomaterials. In this framework, we developed polymer coating zirconia with antibacterial activity using the "grafting from" methodology. First, 1-(4-vinylbenzyl)-3-butylimidazolium chloride monomer was synthesized. Then, the surface modification of zirconia substrates was performed with this monomer via surface-initiated photo atom transfer radical polymerization for antibacterial activity. X-ray photoelectron spectroscopy, ellipsometry, static contact angle measurements, and an atomic force microscope were used to characterize the films for each step of the surface modification. The results revealed that cationic polymers could be successfully deposited on the zirconia surfaces, and the thickness of the grafted layer steadily increased with polymerization time. Finally, the antibacterial adhesion test was used to evaluate the antibacterial activity of the modified zirconia substrates, and we successfully showed the antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa strains.

Diblock bottlebrush polymer in a non-polar medium: Self-assembly, surface forces, and superlubricity

Whilst bottlebrush polymers have been studied in aqueous media for their conjectured role in biolubrication, surface forces and friction mediated by bottlebrush polymers in non-polar media have not been previously reported. Here, small-angle neutron scattering (SANS) showed that a diblock bottlebrush copolymer (oligoethyleneglycol acrylate/ethylhexyl acrylate; OEGA/EHA) formed spherical core-shell aggregates in n-dodecane (a model oil) in the polymer concentration range 0.1-2.0 wt%, with a radius of gyration Rg ∼ 7 nm, comprising 40-65 polymer molecules per aggregate. The surface force apparatus (SFA) measurements revealed purely repulsive forces between surfaces bearing inhomogeneous polymer layers of thickness L ∼ 13-23 nm, attributed to adsorption of a mixture of polymer chains and surface-deformed micelles. Despite the surface inhomogeneity, the polymer layers could mediate effective lubrication, demonstrating superlubricity with the friction coefficient as low as µ ∼ 0.003. The analysis of velocity-dependence of friction using the Eyring model shed light on the mechanism of the frictional process. That is, the friction mediation was consistent with the presence of nanoscopic surface aggregates, with possible contributions from a gel-like network formed by the polymer chains on the surface. These unprecedented results, correlating self-assembled polymer micelle structure with the surface forces and friction the polymer layers mediate, highlight the potential of polymers with the diblock bottlebrush architecture widespread in biological living systems, in tailoring desired surface interactions in non-polar media.

Fabrication of Biologically Inspired Electrospun Collagen/Silk fibroin/bioactive glass composited nanofibrous scaffold to accelerate the treatment efficiency of bone repair

Bone disease and disorder treatment might be difficult because of its complicated nature. Millions of patients each year need bone substitutes that may help them recover quickly from a variety of illnesses. Synthetic bone replacements that mirror the structural, chemical, and biological features of bone matrix structure will be very helpful and in high demand. In this research, the inorganic bioactive glass nanoparticles matrixed with organic collagen and silk fibroin structure (COL/SF/CaO-SiO₂) were used to create multifunctional bone-like fibers in this study, which we describe here. The fiber structure is organized in a layered fashion comparable to the sequence in which apatite and neo tissue are formed. The amino groups in COL and SF combined with CaO-SiO₂ to stabilize the resulting composite nanofiber. Morphological and functional studies confirmed that crystalline CaO-SiO₂ nanoparticles with average sizes of 20 ± 5 nm are anchored on a 115 ± 10 nm COL/SF nanofiber matrix. X-ray photoelectron spectroscopic (XPS) results confirmed the presence of C, N, O, Ca, and Si in the composite fiber with an atomic percentage of 59.46, 3.30, 20.25, 3.38 and 13.61%. respectively. The biocompatibility examination with osteoblast cells (Saos-2) revealed that the CAL/SF/CaO-SiO₂ composite nanofiber had enhanced osteogenic activity. Finally, when the CAL/SF/CaO-SiO₂ composite nanofiber scaffolds were used to treat an osteoporotic bone defect in a rat model, the composite nanofiber scaffolds significantly promoted bone regeneration and vascularization. This novel fibrous scaffold class represents a potential breakthrough in the design of advanced materials for complicated bone regeneration.

In Situ GISAXS Observation and Large Area Homogeneity Study of Slot-Die Printed PS-b-P4VP and PS-b-P4VP/FeCl3 Thin Films

Mesoporous hematite (α-Fe₂O₃) thin films with high surface-to-volume ratios show great potential as photoelectrodes or electrochemical electrodes in energy conversion and storage. In the present work, with the assistance of an up-scalable slot-die coating technique, locally highly ordered α-Fe₂O₃ thin films are successfully printed based on the amphiphilic diblock copolymer poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) as a structure-directing agent. Pure PS-b-P4VP films are printed under the same conditions for comparison. The micellization of the diblock copolymer in solution, the film formation process of the printed thin films, the homogeneity of the dry films in the lateral and vertical direction as well as the morphological and compositional information on the calcined hybrid PS-b-P4VP/FeCl₃ thin film are investigated. Because of convection during the solvent evaporation process, a similar dimple-type structure of vertically aligned cylindrical PS domains in a P4VP matrix developed for both printed PS-b-P4VP and hybrid PS-b-P4VP/FeCl₃ thin films. The coordination effect between the Fe³⁺ ions and the vinylpyridine groups significantly affects the attachment ability of the P4VP chains to the silicon substrate. Accordingly, distinct feature sizes and homogeneity in the lateral direction, as well as the thicknesses in the perpendicular direction, are demonstrated in the two printed films. By removing the polymer template from the hybrid PS-b-P4VP/FeCl₃ film at high temperature, a locally highly ordered mesoporous α-Fe₂O₃ film is obtained. Thus, a facile and up-scalable printing technique is presented for producing homogeneous mesoporous α-Fe₂O₃ thin films.