Synthesis,Characterization, and In Vitro Antimicrobial Activity of Methyleneamine‐Linked Bis‐heterocycles

A new class of methyleneamine‐linked bis‐heterocycles that exhibit antimicrobial activity was synthesized. Bromination of 1 followed by condensation with thiourea gave 3 . The reaction of 3 with propargyl bromide in dry toluene under inert atmosphere led to the formation of 4 . Its subsequent reaction with different nitrile oxides using CuSO₄.5H₂O–sodiumascorbate system in a 2:1 mixture of water and tert‐butyl alcohol yielded the title compounds 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h , 6i , 6j , 6k , 6l in good yields. The identities of these compounds were confirmed following elemental analysis, IR, ¹H, ¹³C NMR, and mass spectral studies. All the title compounds exhibited pronounced in vitro antibacterial and antifungal activities.     

Liquid crystalline banana‐shaped monomers derived from 2,7‐naphthalene: synthesis and properties

Three banana‐shaped monomers, i.e. 2,7‐naphthalene bis[4‐(4‐allyloxyphenylazo)‐benzoate], 2,7‐naphthalene bis[4‐(4‐allyloxy‐3‐fluorophenylazo)benzoate] and 2,7‐naphthalene bis{4‐[4‐(10‐undecenyloxy)phenylazo]benzoate}, containing azobenzene as side arms, 2,7‐dihydroxynaphthalene as central units and terminal double bonds as polymerisable functional groups, were synthesised and their mesophase behaviour investigated. Polarizing optical microscopy and DSC measurements reveal that all compounds exhibit nematic mesophases. The absorption spectrum of the trans‐azobenzene groups displays a high‐intensity π–π* transition at about 365 nm and a low‐intensity n–π* transition at around 450 nm for all compounds. Hence, photochromism can be achieved by the introduction of the azo linkage to banana‐shaped liquid crystals molecules.     

Mechanism of structure formation of microbial cellulose during nascent stage

The structure of microbial cellulose (MC) produced by Acetobacter xylinum was studied in presence of Fluorescent Brightener, Direct Blue 1, 14, 15, 53, Direct Red 28, 75 and 79, as probe. X-ray diffraction pattern of the product showed that it was a crystalline complex of dye and cellulose. The product has the structure in which the monomolecular layer of the dye molecule is included between the cellulose sheets corresponding to the ( $ 1\bar{1}0 $ ) planes of microbial cellulose. As a result of dye inclusion, d-spacing of lower angle plane (100) of products becomes 8.0–8.8 Å instead of 6.1 Å of MC. The d-spacing for the higher angle plane must be (010) plane due to stronger van der Waals forces between the pyranose rings which reduced 5.3 Å space of (110) plane of MC to 3.9–4.5 Å in the product. However, cellulose regenerated from FB, DR28 products was cellulose I and IV, respectively, and that from each DB1, 14, 15, 53, DR75 and 79 products was cellulose II. Solid state ¹³C NMR and deuteration-IR showed the product was non-crystalline which was contrasted to X-ray results. The regenerated celluloses were cellulose I_β, IV_I and II, respectively. Thus the structure of the product depends on the characteristics of dye which affects the conformation of cellulose at the nascent stage by the direct interaction with cellulose chains. The different regenerated celluloses as well as different fine structure in the same cellulose allomorph were produced depending mainly on number and position of the sulfonate groups in the dye.     

ADSORPTION OF METAL IONS ON STEARIC ACID-NONADECANE PARTICLES IN AQUEOUS SOLUTION

The adsorption of metal ions at the stearic acid/electrolyte and nnonadccane-stearic acid mixture/electrolyte interface was investigated by means of the potentiometric titration, zeta potential and adsorption measurements. It was found that the studied colloidal suspensions exhibited an adsorption affinity towards multivalent metal ions. The adsorption of Ca²⁺, Cd²⁺ and Al³⁺ ions caused a strong decrease of surface charge density and zeta potential values in this systems. The adsorption reactions occur by way of cation exchange with protons from two surface carboxyl groups. Al high metal concentrations, in adsorption reactions there are involved also carboxyl groups from the subsurface layer. On the basis of the adsorption data, the cation surface complexation constants were calculated by Shindler's method.     

Oxymatrine Loaded Cross-Linked PVA Nanofibrous Scaffold: Design and Characterization and Anticancer Properties

This study focuses on the fabrication, characterization and anticancer properties of biocompatible and biodegradable composite nanofibers consisting of poly(vinyl alcohol) (PVA), oxymatrine (OM), and citric acid (CA) using a facile and high-yield centrifugal spinning process known as Forcespinning. The effects of varying concentrations of OM and CA on fiber diameter and molecular cross-linking are investigated. The morphological and thermo-physical properties, as well as water absorption of the developed nanofiber-based mats are characterized using microscopical analysis, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. In vitro anticancer studies are conducted with HCT116 colorectal cancer cells. Results show a high yield of long fibers embedded with beads. Fiber average diameters range between 462 and 528 nm depending on OM concentration. The thermal analysis results show that the fibers are stable at room temperature. The anticancer study reveals that PVA nanofiber membrane with high concentrations of OM can suppress the proliferation of HCT116 colorectal cancer cells. The study provides a comprehensive investigation of OM embedded into nanosized PVA fibers and the prospective application of these membranes as a drug delivery system.     

Cement Composites with Carbon-Based Nanomaterials for 3D Concrete Printing Applications – A Review

3D concrete printing (3DCP) is an emerging additive manufacturing technology in the construction industry. Its challenges lie in the development of high-performance printable materials and printing processes. Recently developed carbon-based nanomaterials (CBNs) such as graphene, graphene oxide, graphene nanoplatelets, and carbon nanotubes, have various applications due to their exceptional mechanical, chemical, thermal, and electrical characteristics. CBNs also have found potential applications as a concrete ingredient as they enhance the microstructure and modify concrete properties at the molecular level. This paper focuses on state-of-the-art studies on CBNs, 3DCP technology, and CBNs in conventional and 3D printable cement-based composites including CBN dispersion techniques, concrete mixing methods, and fresh and hardened properties of concrete. Furthermore, the current limitations and future perspectives of 3DCP using CBNs to produce high-quality composite mixtures are discussed.     

3D Printable Geopolymer Composites Reinforced with Carbon-Based Nanomaterials – A Review

Three-dimensional (3D) geopolymer printing (3DGP) technology is a rapidly evolving digital fabrication method used in the construction industry. This technology offers significant benefits over 3D concrete printing in terms of energy saving and reduced carbon emissions, thus promoting sustainability. 3DGP technology is still evolving, and researchers are striving to develop high-performance printable materials and different methods to improve its robustness and efficiency. Carbon-based nanomaterials (CBNs) with beneficial properties have a wide range of applications in various fields, including as concrete/geopolymer systems in construction. This paper comprehensively reviews the research progress on carbon-based nanomaterials (CBNs) used to develop extrusion-based 3D geopolymer printing (3DGP) technology, including dispersion techniques, mixing methods, and the materials′ performance. The rheological, mechanical, durability, and other characteristics of these materials are also examined. Furthermore, the existing research limitations and the prospects of using 3DGP technology to produce high-quality composite mixtures are critically evaluated.     

Production of textile filaments from carboxymethylated cellulosic pulps

Cellulose - Textile filaments were fabricated from a solution obtained from carboxymethylated cellulose dissolved in aqueous NaOH solution, by wet spinning in an acid coagulation bath. Spinning is...     

Reactivity Ratios and Sequence Distribution Characterization by Quantitative 13C NMR for RAFT Synthesis of Styrene‐Acrylonitrile Copolymers

The kinetics and reactivity ratios of styrene‐acrylonitrile (SA) copolymerization have been studied extensively in bulk and in a variety of solution media using conventional free radical polymerizations (FRPs). Due to the significant difference in the two reactivity ratios for this monomer pair, at certain feed ratios the copolymers display composition drift with conversion due to monomer depletion. In this study, the kinetics of SA copolymerization using Reversible Addition‐Fragmentation Chain Transfer (RAFT) has been studied in bulk at 80 °C. The reactivity ratios for the terminal model were calculated from the comonomer sequence distributions for the RAFT process at low conversion for nine different compositions and found to be in the same range as those reported for conventional FRP of SA. The changes in the composition and sequence distribution with conversion were studied for three feed compositions. The copolymers show compositional drift with conversion, except at the azeotropic composition, and match the predictions from the reactivity ratios obtained at low conversion. From quantitative ¹³C NMR the triad distributions of these copolymers were estimated and found to match the predicted triad distributions as conversion increased. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 919–927