Vanillin–Schiff’s bases as organic thermal stabilizers and co-stabilizers for rigid poly(vinyl chloride)

Synthesis, computational, anticancerous and antiproliferative effects of some copper, manganese and zinc complexes with ligands derived from symmetrical 2,2’-diamino-4,4’-dimethyl-1,1’-biphenyl-salicylaldehyde

Four new symmetrical Schiff bases derived from 2,2’-diamino-4,4’-dimethyl-1,1’-biphenyl-salicylaldehyde have been synthesized and characterized by elemental analysis and different spectroscopic techniques. The reaction of 2,2’-diamino-4,4’-dimethyl-1,1’-biphenyl with two equivalents of 5-tert-butyl-, 3,5-dinitro-, 3,5-dibromo- and 3-tert-butyl-salicylaldehyde yielded 2,2’-bis(5-tert-butyl-salicylideneamino)-4,4’-dimethyl-1,1’-biphenyl (A1) as well as the 3,5-dinitro- (A2), 3,5-dibromo- (A3) and 3-tert-butyl- (A4) substituted derivatives. The tetradentate ligands were then reacted with copper-, manganese- and zinc-acetate producing the tetra-coordinate metal complexes which were characterized by FTIR, UV-Visible spectroscopy, magnetic susceptibility and elemental analysis. Zinc complexes were characterized by 1H-NMR spectroscopy. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level of theory were carried out to fully optimize and examine the molecular geometries of complexes. Subsequently, IR vibrational and UV-Vis absorption spectra were computed and correlated with the observed values and the results are in good agreement with the experimental data. The anticancerous and antiproliferative activity of the A3 ligand and its metal complexes were determined.

Cooperative crystallization effect in the formation of sonochemically grafted active materials based on polysaccharides

The current study explores the formation of active eco-friendly materials capable of preventing microbial contamination using in situ ultrasonic grafting of vanillin, curcumin and a curcumin-vanillin mixture on the surfaces of carboxymethylcellulose (CMC) and chitosan films. Spectroscopic, microscopic, physical and mechanical studies revealed that the films grafted with curcumin-vanillin mixture demonstrate improved mechanical properties and higher degree of order. The bioactivity of the prepared films was tested on food model, fresh-cut melons and films with a deposited curcumin-vanillin mixture showed superior antibacterial properties. For instance, this mixture-grafted on CMC films demonstrated a total inhibition of yeast/mold proliferation during 12 days. The HR-SEM studies of the mixture-grafted films revealed the presence of crystalline structures. Cooperative crystallization effect between the curcumin (the crystal maker) and the volatile vanillin is suggested to be responsible for the observed effects. According to our knowledge, this is the first usage of co-crystallization method in surface deposition. The results point out to a general strategy of combining a crystal maker agent with a volatile active agent during in situ sonochemical deposition to form bioactive materials that can be further used for food packaging, agriculture, pharmacology and more.

Dechlorination of polyvinyl chloride electric wires by hydrothermal treatment using K2CO3 in subcritical water

Polyvinyl chloride (PVC) waste generation has significantly increased in recent years and their disposal is considered a major environmental concern. Removal techniques of chlorine from PVC waste are being studied to minimize a negative environmental impact. In this work, the use of K₂CO₃ as an alkaline additive to improve the dechlorination efficiency (DE) in the hydrothermal degradation of PVC wires was studied. Different experiments were carried out varying both temperature (175, 200, 225, 235 and 250 °C) and K₂CO₃ concentration (0.025, 0.050 and 0.125 M), using a solid/liquid ratio of 1:5 in order to determine the evolution of the dechlorination efficiency with time. About 4.66, 21.1, 24.4, 45.7 and 92.6 wt% of chlorine in PVC wire was removed during hydrothermal dechlorination (HTD) with an additive/chlorine ratio of 1:25 (K₂CO₃ solution of 0.050 M) at 175, 200, 225, 235 and 250 °C, respectively. Optimal additive/chlorine ratio decreased to 1:50 (K₂CO₃ solution of 0.025 M) at 250 °C, obtaining a dechlorination degree of 99.1% after 4 h without the need of metallic catalysts. Concerning the solid phase behavior during dechlorination, a linear correlation between the DE reached and the weight loss of PVC was found.

Synthesis, characterization and corrosion inhibition potential of two novel Schiff bases on mild steel in acidic medium

This study reports the synthesis of new Schiff bases namely 5-((4-chloro-3-nitrophenylimino)methyl)-2-methoxyphenol and 2-(4-hydroxy-3-methoxybenzylidineamino)-4-nitrophenol using solid–liquid phase equilibrium diagram and their characterization.

Biomass Vanillin-Derived Polymeric Microspheres Containing Functional Aldehyde Groups: Preparation, Characterization, and Application as Adsorbent

The contribution reports the first polymeric microspheres derived from a biomass, vanillin. It reacted with methacryloyl chloride, providing monomer vanillin methacrylate (VMA), which underwent suspension polymerization in aqueous media and yielded microspheres in high yield (>90 wt %). By controlling the N2 bubbling mode and by optimizing the cosolvent for dissolving the solid monomer, the microspheres were endowed with surface pores, demonstrated by SEM images and mercury intrusion porosimetry measurement. Taking advantage of the reactive aldehyde groups, the microspheres further reacted with glycine, thereby leading to a novel type of Schiff-base chelating material. The functionalized microspheres demonstrated remarkable adsorption toward Cu(2+) (maximum, 135 mg/g) which was taken as representative for metal ions. The present study provides an unprecedented class of biobased polymeric microspheres showing large potentials as adsorbents in wastewater treatment. Also importantly, the reactive aldehyde groups may enable the microspheres to be used as novel materials for immobilizing biomacromolecules, e.g. enzymes.

Synthesis, spectral, crystal structure, thermal behavior, antimicrobial and DNA cleavage potential of two octahedral cadmium complexes: a supramolecular structure

Two new cadmium(II) complexes with the formula of CdL2(NCS)2 and CdL2(N3)2 (in which L is 2,2-dimethyl-N,N'-bis-(3-phenyl-allylidene)-propane-1,3-diamine) have been synthesized and characterized by elemental analysis, molar conductivity measurements, FT/IR, UV-Visible, (1)H and (13)C NMR spectra and X-ray studies. The crystal structure analysis of CdL2(NCS)2 indicated that it crystallizes in orthorhombic system with space group of Pbca. Two Schiff base ligands are bonded to cadmium(II) ion as N2-donor chelate. Coordination geometry around the cadmium ion was found to be partially distorted octahedron. The Cd-Nimine bond distances are found in the range of 2.363(2)-2.427(2)Å while the Cd-Nisothiocyanate bond distances are 2.287(2)Å and 2.310(2)Å. The existence of C-H⋯π and C-H⋯S interactions in the CdL2(NCS)2 crystal leads to a supramolecular structure in its network. Then cadmium complexes were screened in vitro for their antibacterial and antifungal activities against two Gram-negative and two Gram-positive bacteria and also against Candida albicans as a fungus. Moreover, the compounds were subjected for DNA-cleavage potential by gel electrophoresis method. Finally thermo-gravimetric analysis of the complexes was applied for thermal behavior studies and then some thermo-kinetics activation parameters were evaluated.

Novel antimicrobial organic thermal stabilizer and co-stabilizer for rigid PVC

Biologically active N-benzoyl-4-(N-maleimido)-phenylhydrazide (BMPH) was synthesized and its structure was confirmed by elemental analysis and various spectral tools. It was examined as a thermal stabilizer and co-stabilizer for rigid poly (vinyl chloride) at 180 °C in air. Blending BMPH with reference samples in different ratios greatly lengthens the thermal stability value and improves the extent of discoloration of PVC. TGA confirmed the improved stability of PVC in presence of the investigated organic stabilizer. GPC measurements were done to investigate the changes occurred in the molecular masses of the degraded samples of blank PVC and PVC in presence of the novel stabilizer. BMPH showed good antimicrobial activity towards two kinds of bacteria and two kinds of fungi.