Intramolecular hydrogen-bond-assisted planarization of asymmetrically functionalized alternating phenylene-pyridinylene copolymers

We report on the synthesis and characterization of a series of asymmetrically functionalized amphiphilic polymers with alternating pi-donor units (e.g., substituted benzene) and pi-acceptor units (e.g., pyridine) along the polymer backbone. The purpose of our present work involves incorporation of functional groups along the main chain to form intrachain hydrogen bonds, which promote planarization of the polymer backbone, and to fine-tune the optical properties. The structure-property relationship of polymers P1-P6 was investigated by means of analytical methods, such as FTIR spectroscopy, 1H and 13C NMR spectroscopy, UV/Vis spectroscopy, fluorescence spectroscopy, gel permeation chromatography, thermogravimetric analysis, cyclic voltammetry, and X-ray powder diffraction. All polymers were soluble in common organic solvents, and the optical and fluorescence spectra of the polymers showed significant changes according to the formation (P4, P5) or absence (P6) of intramolecular hydrogen bonding along the polymer backbone. Moreover, the 2,6- or 3,5-linkage of the pyridine rings in P5 and P6, respectively, reduced the conjugation along the polymer backbone and this is reflected in their optical properties. The optical properties of the polymers were influenced by the addition of acid (P1-P6), base (P4-P6), and metal ions (e.g., Cu2+, Fe3+, Ag+, Ni2+, Pd2+, Mn2+, Zn2+, Mg2+, and Pr3+). Such polymers could be used in various applications, including sensors and stimuli-responsive displays.     

On-site polymer-coated hollow fiber membrane microextraction and gas chromatography--mass spectrometry of polychlorinated biphenyls and polybrominated diphenyl ethers

Porous polypropylene hollow fiber membrane coated with a conjugated polymer was used as an on-site sampling device for the extraction of polychlorinated biphenyls and polybrominated biphenyl ethers from coastal sea water samples. The coated hollow fiber membrane was placed in a vial containing the sample, and the target compounds extracted via manual shaking of the vials at the site of sample collection. For each extraction, two fibers were used. After extraction, the fibers with the adsorbed analytes were brought back to the laboratory for further processing. Care was taken to preserve the integrity of the analytes and to avoid contamination during transport; after extraction, the fibers were carefully removed and placed in air-tight crimper vials which were stored in an ice-box. The analytes were desorbed by solvent in the laboratory and analyses were carried out using gas chromatography/mass spectrometry. This method was highly reproducible with relative standard deviations in the range of 1-9%. Recoveries from spiked water samples ranged from 83% to 98%. Low limits of detections between 0.04 and 0.21ngl(-1) were achieved. The extraction efficiency was compared with solid-phase microextraction.     

Surface cationization of cellulose to enhance durable antibacterial finish in phytosynthesized silver nanoparticle treated cotton fabric

Cellulose - Elimination of disease-causing bacteria from cotton fabrics is critically important to control several bacteria-mediated infections in humans. Antibacterial nanoparticles, particularly...     

Synthesis and comparison of the structure–property relationships of symmetric and asymmetric water‐soluble poly(p‐phenylene)s

Sodium salts of water‐soluble polymers poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(hexyloxy)‐1,4‐phenylene]} ( P1 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dodecyloxy)‐1,4‐phenylene]} ( P2 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dibenzyloxy)‐1,4‐phenylene]} ( P3 ), poly[2‐hexyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P4 ), and poly[2‐dodecyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P5 )] were synthesized with Suzuki coupling reactions and fully characterized. The first group of polymers ( P1 – P3 ) with symmetric structures gave lower absorption maxima [maximum absorption wavelength (λ_max) = 296–305 nm] and emission maxima [maximum emission wavelength (λ_em) = 361–398 nm] than asymmetric polymers P4 (λ_max = 329 nm, λ_em = 399 nm) and P5 (λ_max = 335 nm, λ_em = 401 nm). The aggregation properties of polymers P1 – P5 in different solvent mixtures were investigated, and their influence on the optical properties was examined in detail. Dynamic light scattering studies of the aggregation behavior of polymer P1 in solvents indicated the presence of aggregated species of various sizes ranging from 80 to 800 nm. The presence of alkoxy groups and 3‐sulfonatopropoxy groups on adjacent phenylene rings along the polymer backbone of the first set hindered the optimization of nonpolar interactions. The alkyl chain crystallization on one side of the polymer chain and the polar interactions on the other side allowed the polymers ( P4 and P5 ) to form a lamellar structure in the polymer lattice. Significant quenching of the polymer fluorescence upon the addition of positively charged viologen derivatives or cytochrome‐C was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers could be used in the fabrication of biological and chemical sensors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3763–3777, 2006     

Syntheses, structural properties and catecholase activity of copper(II) complexes with reduced Schiff base N-(2-hydroxybenzyl)-amino acids

A number of dicopper(II) complexes of reduced Schiff base ligands, N-(2-hydroxybenzyl)-amino acids [Cu2L2(H2O)x].yH2O (L = Sgly (1), D-Sala (2), L-Sala (3), DL-Sala (4), Sab2 (5), Sbal (6), Sab4 (7), Sval (8), Shis (9), Styr (10) and Stryp (11), x= 0-2 & y= 0-2) have been synthesized, and the solid-state structures of, and have been determined. The compounds and are binuclear in which the Cu(II) centres have square-pyramidal geometry with apical sites occupied by aqua ligands. In and one axial site is occupied by water and the other by an oxygen atom of the carboxylate group from the adjacent dimer through oxygen atoms to form 1D helical polymer. Variable temperature magnetic measurements of the dimer and helical polymer showed that they are typical for moderately strong antiferromagnetic coupling. All the complexes show significant catalytic activity on the oxidation of 3,5-di-tert-butylcatechol. The activity measured in terms of Kcat in the range 199-3800 h(-1) has been found to follow the order: 7>6>8>3>5 approximately 2 approximately 1>4 >10 >9 >11. The catalytic activity is found to increase with increasing the length of the methylene side chain of the amino acid in the reduced Schiff base ligands.     

Infinite three-dimensional polymeric metalloporphyrin network via six-coordinate Zn(II) and two axial oxygen donors

[structure: see text]. An X-ray crystallographic study of zinc(II) 5,15-di-(2-methoxymethylphenyl)-porphyrin indicates that it forms a coordination polymer through ligation of the ether oxygen atoms on the porphyrin peripheries to the metal centers of two identical adjacent porphyrins. This gives a novel extensively linked, three-dimensional polymeric structure in which the zinc(II) metal forms a six-coordination center. The uniquely structured network has cavities between 4.81 and 9.27 angstroms, which makes it resemble molecular sieve materials.