Influence of Particle Size and Loading on Particle Accessibility in Electrospun Poly(ethylene oxide) and ZIF‑8 Composite Fibers: Experiments and Theory

Developing electrospun nanofiber/nanoparticle composites (ENNCs) is an emerging strategy for immobilizing functional particles for a variety of applications. The radial location of the particle along the fiber, either at the surface or in the bulk, has implication into the resulting properties. To explore particle location along fibers, ZIF-8 impregnated poly­(ethylene oxide) (PEO) nanofibers are formed by electrospinning particle suspensions. Fibers impregnated with two different ZIF-8 particle sizes (200 nm and 12.5 μm) were electrospun and shown by nitrogen porosimetry to be nearly completely wrapped by PEO in each case at loadings near 10 wt %. This was favorably compared to developed theory of polymeric membrane encapsulated particles and extended to other electrospun fiber/particle composites through a brief literature review. ENNCs with varying loadings of nanosized ZIF-8 particles were then fabricated and tested with nitrogen porosimetry to find that the particles became available for adsorption at the surface of the fibers starting from 25 wt % (28 vol %) loading. This suggests that the particles are kinetically trapped at this loading level since, if allowed to exhibit random close-packing, the ZIF-8 would be expected to fully imbedded inside the fibers up to 56 vol % loading

Hierarchical Self-Organization and Uniaxial Alignment of Well Synthesized Side-Chain Discotic Liquid Crystalline Polymers

Liquid crystalline polymers (LCPs) combine the attributes of liquid crystals and polymers, while discotic LCPs have been less developed in sharp contrast to their calamitic counterparts mainly due to lack of suitable discotic LCP materials. Here we successfully prepared a series of well-defined triphenylene (TP) based discotic LC polyacrylates via reversible addition–fragmentation chain-transfer (RAFT) polymerization for the first time, and through a combination of multiple analysis techniques and phase transition kinetics study, a remarkable molecular weight effect or polymer effect at a critical degree of polymerization (DP) around 20 has been disclosed. Moreover, the first proposed discrete columnar stacks (DCS) based hierarchical self-organization model accounts well for the formation and transformation of ordered hexagonal columnar lattice Col_ho dominated by side-chain TP stacking and oblique columnar superlattice Col_ob‑s induced by compaction and ordering of polymer backbones. The in-depth understanding of their superstructures and readily achieved uniaxial alignment pave the way for the rational design and preparation of such kind of solution processable cutting-edge polymeric semiconducting materials and may boost various fascinating optoelectronic applications

Green Fabrication of Porous Adsorbent with Structural Evolution of Mixed-Dimension Attapulgite Clay for Efficient Removal of Methylene Blue and Sustainable Utilization

In recent years, a variety of materials have been developed for water treatment, but green preparation and clean regeneration of absorbent materials have always neglected. Herein, porous materials were fabricated based on clean aqueous foam stabilized by natural plants Sapindus mukorossi (S. mukorossi) and mixed-dimensional attapulgite (MDAPT) clay. The effect of crystal defects of MDAPT clay on material preparation was investigated by the acid etching technique. The maximum adsorption capacity of the porous adsorbent prepared by the foam template for methylene blue was up to 847.7 mg/g, and the removal rate was >98% at ambient concentration. More importantly, the waste adsorbent was recycled for resource regeneration. The waste adsorbents were used as raw material to produce mineral biochar by a carbonization method for soil improvement. When the mineral biochar content was 1.5%, the pH of the soil increased from 4.51 to 6.36, and the electrical conductivity increased from 0.48 to 1.35 mS/cm. As a result of the improvement in soil structure and properties, the grown cabbage showed a significant increase in weight, length, and chlorophyll content. In conclusion, this work provides a sustainable idea for the green preparation of absorbent materials and for the recycling and reuse of waste materials

Presentation1_Formation and Coloring Mechanism of Typical Aluminosilicate Clay Minerals for CoAl2O4 Hybrid Pigment Preparation.pdf

<p>Different kinds of aluminosilicate minerals were employed to fabricate CoAl₂O₄ hybrid pigment for studying its formation and coloring mechanism. It revealed that the color of the obtained hybrid pigments was determined by the content of Al₂O₃ and lightness of clay minerals. The higher the Al₂O₃ content and the lightness of clay minerals, the better the color parameters of hybrid pigments. During the preparation of hybrid pigments, CoAl₂O₄ nanoparticles were confined to be loaded on the surface of the aluminosilicate minerals, which effectively prevented from the aggregation and the size increase of CoAl₂O₄ nanoparticles. What's more, aluminosilicate mineral might be an ideal natural aluminum source to compensate the aluminum loss due to the dissolution of Al(OH)₃ at alkaline medium during precursor preparation, keeping an optimum molar ratio of Co²⁺/Al³⁺ for formation of spinel CoAl₂O₄ pigments in the process of high-temperature crystallization.</p

Well-Organized Columnar Superlattices via Positive Coupling between Polymer Backbone and Discotic Side Groups

Very little is known about some fundamental issues such as the spacer length influence and molecular weight (MW) effect of discotic liquid crystalline polymers (DLCPs), despite the elucidation of such aspects are of crucial importance for their structure tuning and device performance. Here in this article, a systematic comparative study has been conducted to investigate the MW effect and especially gain a deeper insight into the spacer length influence of side-chain DLCPs based on a homologous series of well-defined discotic liquid crystalline polyacrylates with triphenylene (TP) side groups of variant spacer lengths. The series DLCPs of shorter spacers display various well-organized columnar superlattices based on multicolumn bundles organization with “coordination number” from two to six through individual discogens or discrete columnar stack (DCS)-based intracolumnar stacking modes. It is disclosed for the first time that the positive coupling effect (PCE) prevails in side-chain DLCPs, and proper coupling between discotic side groups and polymer backbone is desirable and required for achieving well-organized ordered columnar mesophases, in striking contrast with the renowned classical spacer decoupling principle directing the fruitful exploration of their side-chain calamitic counterparts for several decades. These findings are inspiring for in-depth understanding of self-assembly of aromatic interactions involved complex functional chemical and biological systems and especially opening an avenue for rational design and synthesis of well-controlled side-chain DLCPs for low-cost solution processable optoelectronic device applications

Triphenylene-Based Side Chain Liquid Crystalline Block Copolymers Containing a PEG block: Controlled Synthesis, Microphase Structures Evolution and Their Interplay with Discotic Mesogenic Orders

Triphenylene (TP) derivatives are typical and probably the most widely studied discotic liquid crystalline (DLC) materials. Through polymer analogous reactions to attach TP mesogens to the well-synthesized poly­(ethylene glycol)-<i>b</i>-poly­(2-hydroxyethyl acrylate) (PEG–PHEA) by ATRP, a series of well-defined side chain DLC diblock copolymers PEG–poly­(TPm) (<i>m</i> = 6 or 10) with DLC block weight fraction (<i>f</i>_w,DLC) ranging from 37% to 90% have been successfully prepared with narrow molecular weight distribution (PDI ≤ 1.11). An intriguing microphase-separated superstructure evolution and the correlation between overall morphologies and discotic mesogenic orders as a function of <i>f</i>_w,DLC and temperature have been demonstrated by combination of DSC, POM, and variable temperature SAXS/WAXS. Those copolymers with lower DLC contents (<i>f</i>_w,DLC = 37% and 43%) and at lower temperatures formed lamellar structures of variant periods and underwent order–order transitions upon PEG region crystallization at 45 °C and different discotic mesophases of N_D or N_col transition at about 25 °C. For the copolymer with intermediate <i>f</i>_w,DLC = 62%, a high temperature hexagonal packed cylinder (HPC) structure of amorphous PEG nanocylinders in the matrix of DLC was formed above 35 °C, while upon cooling below 35 °C it turned into a mixed lamellar structure with PEG region crystallization. The higher <i>f</i>_w,DLC (67% ∼ 80%) copolymers exhibited HPC structures with the DLC matrix showing N_col or N_D mesophases. For copolymers with the highest <i>f</i>_w,DLC around 90%, an overall N_D phase was developed in sharp contrast to the ordered columnar phase formed by their corresponding DLC homopolymers, which was quite inspiring and might suggest another pathway of attaining this important nematic discotic phase through introducing a suitable copolymerized block. The better understanding of the interrelation of microstructures and discotic mesogenic orders constitutes the key basis for utilizing such type of organic semiconductor materials and could help to guide the design of complex DLC polymer materials with hierarchical structures for variant applications

Modeling Nanoparticle Dispersion in Electrospun Nanofibers

The quality of nanoparticle dispersion in a polymer matrix significantly influences the macroscopic properties of the composite material. Like general polymer–nanoparticle composites, electrospun nanofiber nanoparticle composites do not have an adopted quantitative model for dispersion throughout the polymer matrix, often relying on a qualitative assessment. Being such an influential property, quantifying dispersion is essential for the process of optimization and understanding the factors influencing dispersion. Here, a simulation model was developed to quantify the effects of nanoparticle volume loading (ϕ) and fiber-to-particle diameter ratios (<i>D</i>/<i>d</i>) on the dispersion in an electrospun nanofiber based on the interparticle distance. A dispersion factor is defined to quantify the dispersion along the polymer fiber. In the dilute regime (ϕ < 20%), three distinct regions of the dispersion factor were defined with the highest quality dispersion shown to occur when geometric constraints limit fiber volume accessibility. This model serves as a standard for comparison for future experimental studies and dispersion models through its comparability with microscopy techniques and as a way to quantify and predict dispersion in electrospinning polymer–nanoparticle systems with a single performance metric

Hierarchical Pore Structures and High ZIF‑8 Loading on Matrimid Electrospun Fibers by Additive Removal from a Blended Polymer Precursor

A novel method for increasing the effective nanoparticle loading in electrospun fibers is presented involving the electrospinning of polymer blends with suspended ZIF-8 crystals. Initially, varying ratios of Matrimid 5218 and poly­(ethylene oxide) (PEO) are electrospun, followed by methanol washes to remove PEO to form porous Matrimid nanofibers. After an optimum surface area is found from the ratio of 1:1 Matrimid:PEO by weight, the metal-organic-framework ZIF-8 is suspended in the polymer blend and electrospun to form ZIF-8 impregnated fibers. After PEO removal from ZIF-8 impregnated fibers, it is found that the ZIF-8 remains in the porous fibers, resulting in drastic increases in ZIF-8:nanofiber loadings, increased gas uptake, and increased accessible ZIF-8 within the fibers. This method is anticipated to work for many different nanoparticle–polymer systems, having implications in the fields of filtration, sensing, catalysis, and adsorption

Boronic Acid Library for Selective, Reversible Near-Infrared Fluorescence Quenching of Surfactant Suspended Single-Walled Carbon Nanotubes in Response to Glucose

We describe the high-throughput screening of a library of 30 boronic acid derivatives to form complexes with sodium cholate suspended single-walled carbon nanotubes (SWNTs) to screen for their ability to reversibly report glucose binding <i>via</i> a change in SWNT fluorescence. The screening identifies 4-cyanophenylboronic acid which uniquely causes a reversible wavelength red shift in SWNT emission. The results also identify 4-chlorophenylboronic acid which demonstrates a turn-on fluorescence response when complexed with SWNTs upon glucose binding in the physiological range of glucose concentration. The mechanism of fluorescence modulation in both of these cases is revealed to be a photoinduced excited-state electron transfer that can be disrupted by boronate ion formation upon glucose binding. The results allow for the elucidation of design rules for such sensors, as we find that glucose recognition and transduction is enabled by para-substituted, electron-withdrawing phenyl boronic acids that are sufficiently hydrophobic to adsorb to the nanotube surface

Attapulgite Doped with Fe and Cu Nanooxides as Peroxidase Nanozymes for Antibacterial Coatings

The search for low-cost, highly efficient, and stable nanozymes mimicking peroxidase (POD) enzymes remains a great challenge in the development of valuable antibacterial applications. Herein, a natural attapulgite (ATP)-supported Fe and Cu oxide with mixed valences (Fe-Cu/ATP) is reported as an efficient nanozyme by a feasible impregnation method. The obtained Fe-Cu/ATP nanozyme with a large specific area and high dispersity can effectively catalyze the hydrogen peroxide (H2O2) decomposition, exhibiting enhanced POD-like activity compared with Fe/ATP, Cu/ATP, and pristine ATP. In addition, the Fe-Cu/ATP showed high stability and reusability. Through further combination with the density functional theory calculation, the electron density of the ATP surface is increased by simultaneously introducing Fe and Cu dopants. Thus, Fe-Cu/ATP possesses excellent antibacterial properties including a short-time effect depending on the POD-like activity with H2O2 and a long-term effect generated by the metal without H2O2. Finally, a coating desktop and an antibacterial fabric were delicately designed and fabricated by loading Fe-Cu/ATP onto polyethylene and a fabric surface, showing the enormous potential of Fe-Cu/ATP as building and medical functional coatings. This study provides a rational way to design natural mineral nanozymes for promising antibacterial applications