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Proton Nuclear Magnetic Resonance (proton + nuclear_magnetic_resonance)
Terms modified by Proton Nuclear Magnetic Resonance Selected AbstractsFree radical graft copolymerization of poly(n -butyl methacrylate) and poly(butyl acrylate) onto chlorinated rubber: Characterization and mechanical properties,ADVANCES IN POLYMER TECHNOLOGY, Issue 2 2004Shanaz Ahmed Abstract Graft copolymerization of n -butyl methacrylate and butyl acrylate onto chlorinated rubber was carried out in solution medium (xylene) using benzoyl peroxide as initiator. The chlorinated rubber-g-(n -butyl methacrylate- co -butyl acrylate) (CR-g-nBMA- co -BA) was isolated from the copolymerization mixture by extracting with isopropyl ether. Infrared (FT-IR) spectra, proton nuclear magnetic resonance (1H NMR) and thermogravimetric analysis of the graft copolymer showed the occurrence of grafting. Percent grafting and grafting efficiency calculated under different experimental conditions are discussed. The mechanical properties of the grafted CR films were studied under different strain rates. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 103,110, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20003 [source] Kinetics and mechanism of the radical copolymerization of 4-vinyl pyridine with methyl acrylate initiated by p -acetylbenzylidene triphenylarsonium ylideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009S. P. Tiwari Abstract The free-radical copolymerization of 4-vinyl pyridine (4-VP) with methyl acrylate (MA) initiated by p -acetylbenzylidene triphenylarsonium ylide at 60 ± 0.1°C with dioxane as an inert solvent yielded random copolymers. The kinetic equation was Rp , [Ylide]0.83[4-VP]0.33 [MA]0.40 (where Rp is the rate of polymerization); in other words, the system followed nonideal kinetics. The values of the energy of activation and kp2/kt (where kp is the rate constant of propagation and kt is the rate constant of termination) were 23.21 kJ/mol and 1.212 × 10,5 mol L,1 s,1, respectively. The reactivity ratios calculated with the Kelen,Tüdos method were 0.14 ± 0.0075 for 4-VP and 0.56 ± 0.0078 for MA. The copolymers were characterized with Fourier transform infrared, proton nuclear magnetic resonance, differential scanning calorimetry, and electron spin resonance methods. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Preparation and in vitro release of D,L -tetrahydropalmatine-loaded graft copolymer nanoparticlesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Yinglei Zhai Abstract D,L -tetrahydropalmatine (THP)-loaded poly{[,-maleic anhydride-,-methoxy-poly(ethylene glycol)]- co -(ethy cyanoacrylate)} (PEGECA) amphiphilic graft copolymer nanoparticles (PEGECAT NPs) were prepared by the nanoprecipitation technique. The effects of solvent property, temperature, copolymer composition, and drug feeding on the drug-loaded amount and size of PEGECAT NPs were investigated. The morphological structure of PEGECAT NPs was characterized by transmission electron microscopy (TEM), proton nuclear magnetic resonance (1H NMR), and the size was measured by laser particle size analyzer (LPSA). In vitro release behaviors of drug from PEGECAT NPs were examined by high-pressure liquid chromatography (HPLC). The results demonstrate that PEGECAT NPs take on a spherical morphology with an inner core and outer shell before and after in vitro release. THP can be incorporated into the hydrophobic core of PEGECAT NPs and the drug-loaded amount is higher than 5%. The release of THP from PEGECAT NPs is initially fast and then slows down. The accumulated release is lower than 40% after 48 h. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis and physical properties of low-molecular-weight redistributed poly(2,6-dimethyl-1,4-phenylene oxide) for epoxy resinJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Hann-Jang Hwang Abstract Low-molecular-weight poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was prepared by the redistribution of regular PPO with 4,4,-isopropylidenediphenol (bisphenol A) with benzoyl peroxide as an initiator in toluene. The redistributed PPO was characterized by proton nuclear magnetic resonance, mass spectra, and Fourier transform infrared spectroscopy. The redistributed PPO oligomers with terminal phenolic hydroxyl groups and low molecular weights (weight-average molecular weight = 800,4000) were used in the modification of a diglycidyl ether of bisphenol A/4,4,-diaminodiphenylmethane network system. The curing behaviors were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The effect of molecular weight and the amount of redistributed PPO oligomers incorporated into the network on the physical properties of the resulting systems were investigated. The thermal properties of the cured redistributed PPO/epoxy resins were studied by dynamic mechanical analysis, thermal mechanical analysis, thermogravimetric analysis, and dielectric analysis. These cured redistributed PPO/epoxy resins exhibited lower dielectric constants, dissipation factors, coefficients of thermal expansion, and moisture absorptions than those of the control diglycidyl ether of bisphenol A based epoxy. The effects of the composition on the glass-transition temperature and thermal stability are discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Properties of styrene-methyl methacrylate grafted DPNR latex at different monomer concentrationsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Siti Hajjar Che Man Abstract The graft copolymerization of styrene and methyl methacrylate (MMA) on to deproteinized natural rubber (DPNR) latex was carried out. The effect of monomer concentrations on grafting efficiency, thermal and mechanical properties was studied. The synthesized graft copolymers were characterized by proton nuclear magnetic resonance (1H NMR) and the highest grafting efficiency was found at 20 wt % monomer concentration. At low monomer concentration (10 wt %) the grafting was not significant and at 30 wt %, the grafting efficiency was slightly decreased. The thermal properties of graft copolymers were analyzed using differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). The degradation temperature (Tdeg) of the graft copolymer was increased with the increase in monomer concentration which indicates the improvement in thermal stability. The DSC result showed improvement in miscibility between the components as the monomer concentration increased. The mechanical properties of gum and filled modified NR were also investigated in terms of tensile strength, tensile modulus and elongation at break. The tensile strength and elongation at break decreased with an increase in monomer concentration while tensile modulus increased as the monomer concentration increased. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Comparative study of the hydrolytic degradation of glycolide/L -lactide/,-caprolactone terpolymers initiated by zirconium(IV) acetylacetonate or stannous octoateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Janusz Kasperczyk Abstract A series of copolymers have been synthesized by the ring-opening polymerization of glycolide, L -lactide, and ,-caprolactone with zirconium(IV) acetylacetonate [Zr(Acac)4] or stannous octoate [Sn(Oct)2] as the catalyst. The resulting terpolymers have been characterized by analytical techniques such as proton nuclear magnetic resonance, size exclusion chromatography, and differential scanning calorimetry. Data have confirmed that Sn(Oct)2 leads to less transesterification of polymer chains than Zr(Acac)4 under similar conditions. The various copolymers have been compression-molded and allowed to degrade in a pH 7.4 phosphate buffer at 37°C. The results show that the degradation rate depends not only on the copolymer composition but also on the chain microstructure, the Sn(Oct)2 -initiated copolymers degrading less rapidly than Zr(Acac)4 -initiated ones with more random chain structures. The caproyl component appears the most resistant to degradation as its content increases in almost all cases. Moreover, caproyl units exhibit a protecting effect on neighboring lactyl or glycolyl units. The glycolyl content exhibits different features: it decreases because of faster degradation of glycolyl units, which are more hydrophilic than caproyl and lactyl ones, remains stable in the case of abundant CGC sequences, which are very resistant to degradation, or even increases because of the formation of polyglycolide crystallites. Terpolymers can crystallize during degradation if the block length of one of the components is sufficiently long, even though they are amorphous initially. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation of poly(amic acid) and polyimide derived from 3,3,,4,4,-benzophenonetetracarboxylic dianhydride with different diamines by microwave irradiationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Quantao Li Abstract Polycondensation-type poly(amic acid) (PAA) was synthesized with 3,3,,4,4,-benzophenonetetracarboxylic dianhydride as a dianhydride monomer and 4,4,-diaminodiphenylmethane and 4,4,-oxydianiline as diamine monomers under microwave irradiation in dimethylformamide. Then, PAA was used to make polyimide (PI) by imidization at a low temperature. The structure and performance of the polymers were characterized with Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H-NMR), viscosity, X-ray diffraction (XRD), and thermogravimetry (TG) curve analyses. The FTIR spectra of the polymers showed characteristic peaks of PI around 1779 and 1717 cm,1. The 1H-NMR spectrum of PAA indicated a singlet at 6.55 ppm assigned to NHCO and a singlet at 10.27 ppm assigned to carboxylic acid protons. The XRD spectrum demonstrated that the obtained PI had a low-order aggregation structure with a d -spacing of 0.5453 nm. The TG results revealed that the PI was thermally stable with 10% weight loss at 565°C in an N2 atmosphere. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Synthesis and characterization of side-chain liquid crystalline ABC triblock copolymers with p -methoxyazobenzene moieties by atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2008Xiaohua He Abstract A series of novel side-chain liquid crystalline ABC triblock copolymers composed of poly(ethylene oxide) (PEO), polystyrene (PS), and poly[6-(4-methoxy-4,-oxy-azobenzene) hexyl methacrylate] (PMMAZO) were synthesized by atom transfer radical polymerization (ATRP) using CuBr/1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) as a catalyst system. First, the bromine-terminated diblock copolymer poly(ethylene oxide)- block -polystyrene (PEO-PS-Br) was prepared by the ATRP of styrene initiated with the macro-initiator PEO-Br, which was obtained from the esterification of PEO and 2-bromo-2-methylpropionyl bromide. An azobenzene-containing block of PMMAZO with different molecular weights was then introduced into the diblock copolymer by a second ATRP to synthesize the novel side-chain liquid crystalline ABC triblock copolymer poly(ethylene oxide)- block -polystyrene- block -poly[6-(4-methoxy-4,-oxy-azobenzene) hexyl methacrylate] (PEO-PS-PMMAZO). These block copolymers were characterized using proton nuclear magnetic resonance (1H NMR) and gel permeation chromatograph (GPC). Their thermotropic phase behaviors were investigated using differential scanning calorimetry (DSC) and polarized optical microscope (POM). These triblock copolymers exhibited a smectic phase and a nematic phase over a relatively wide temperature range. At the same time, the photoresponsive properties of these triblock copolymers in chloroform solution were preliminarily studied. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4442,4450, 2008 [source] Novel temperature- and pH-responsive graft copolymers composed of poly(L -glutamic acid) and poly(N -isopropylacrylamide)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2008Chaoliang He Abstract A series of novel temperature- and pH-responsive graft copolymers, poly(L -glutamic acid)- g -poly(N -isopropylacrylamide), were synthesized by coupling amino-semitelechelic poly(N -isopropylacrylamide) with N -hydroxysuccinimide-activated poly(L -glutamic acid). The graft copolymers and their precursors were characterized, by ESI-FTICR Mass Spectrum, intrinsic viscosity measurements and proton nuclear magnetic resonance (1H NMR). The phase-transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering. The solution behavior of the copolymers showed dependence on both temperature and pH. The cloud point (CP) of the copolymer solution at pH 5.0,7.4 was slightly higher than that of the solution of the PNIPAM homopolymer because of the hydrophilic nature of the poly(glutamic acid) (PGA) backbone. The CP markedly decreased when the pH was lowered from 5 to 4.2, caused by the decrease in hydrophilicity of the PGA backbone. At a temperature above the lower critical solution temperature of the PNIPAM chain, the copolymers formed amphiphilic core-shell aggregates at pH 4.5,7.4 and the particle size was reduced with decreasing pH. In contrast, larger hydrophobic aggregates were formed at pH 4.2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4140,4150, 2008 [source] Thermogelling behaviors of poly(caprolactone- b -ethylene glycol- b -caprolactone) triblock copolymer in the presence of hyaluronic acidJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2008In Yong Kim Abstract In this article, we studied the effect of hyaluronic acid (HA) on thermogelation of poly(caprolactone- b -ethylene glycol- b -caprolactone) (PCL-PEG-PCL) aqueous solution designed as an injectable system for prevention of postsurgical tissue adhesion. The PCL-PEG-PCL triblock copolymers were simply synthesized by ring-opening polymerization of ,-caprolactone (CL) in the presence of PEG as a polymeric initiator. The synthesized copolymers were confirmed by proton nuclear magnetic resonance (1H-NMR) spectroscopy. Possible interactions between HA and PCL-PEG-PCL triblock copolymers in the blend were evaluated by Fourier-transform infrared spectroscopy (FTIR). The effect of HA on the micellization of PCL-PEG-PCL aqueous solution was investigated by dye solubilization method and electrophoretic lighting scattering (ELS) spectrophotometer. Also, the thermogelling behaviors of the PCL-PEG-PCL triblock copolymers in the presence of HA and their mechanism were investigated by test tube inverting method, 13C-NMR, 1H-NMR, Advanced Rheometic Expansion System (ARES), and differential scanning calorimetry (DSC). The PCL-PEG-PCL/HA blend aqueous solutions undergo the sol-gel-sol transition in response to an increase in temperature (10,60 °C) and the gelation of the PCL-PEG-PCL was rather accelerated by HA. Presumably, this accelerated gelation seems to arise from the attractive interactions between them and the effect of chain confinement in the micelle corona region. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3629,3637, 2008 [source] Synthesis and characterization of stimuli-sensitive micro- and nanohydrogels based on photocrosslinkable poly(dimethylaminoethyl methacrylate)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2007Smrati Gupta Abstract The aim of this work was the development of a versatile route for the preparation of temperature- and pH-responsive hydrogels with small dimensions. The copolymerization of N,N -dimethylaminoethyl methacrylate with various amounts (5 and 10 mol %) of dimethylmaleimidoethyl methacrylate in solution with 2,2,-azobisisobutyronitrile as an initiator is described. The structural and molecular characterization of the copolymers was performed with proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet spectroscopy, as well as size exclusion chromatography. Differential scanning calorimetry and thermogravimetry were used for the thermal characterization of the copolymers. Micro- and nanohydrogels of the copolymers were prepared by photocrosslinking. The gels obtained by photocrosslinking were characterized with a combination of surface plasmon resonance and optical waveguide spectroscopy, dynamic light scattering, and scanning electron microscopy. The hydrogels showed temperature- and pH-responsive behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 669,679, 2007 [source] Kevlar and glass fiber treatment for thermoplastic composites by step polycondensationPOLYMER COMPOSITES, Issue 3 2007H. Salehi-Mobarakeh Nylon-6,6 was grafted at the surface of glass and plasma-treated Kevlar fibers for use in nylon,Kevlar thermoplastic composites. Hydroxyl and, in the case of Kevlar, amine end-groups occur at the fibre surface, either as defects or due to the plasma treatment. These were used as anchor points for nylon-6,6 step polycondensation. Fibers were subjected to successive dipping in adipoyl chloride/CH2Cl2 and aqueous hexamethylenediamine solutions in order to attach and grow high molecular weight polymer on the fiber surface. Grafted nylon was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, differential scanning calorimetry and thermogravimetry. It was shown that no backbiting occurred during the first stage of the grafting process and that the polymer quantity increased linearly with number of passes, up to ,50 passes for plasma-treated Kevlar and 100 for glass fibers, after which polymer quantity remained constant, within experimental error, which was attributed to the onset of termination reactions. POLYM. COMPOS., 28:278,286, 2007. © 2007 Society of Plastics Engineers [source] Synthesis and characteristic of polybenzoxazine with phenylnitrile functional groupPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2009Huimin Qi Abstract The phenylnitrile functional benzoxazine monomers, 3-phenyl-3,4-dihydro- 6-nitril-2H-1,3-benzoxazine (NBen-a) and 4,4,-bis(3,4-dihydro-6-nitril-2H-1,3-benzoxazine-3-yl)phenylether (NBen-De), were synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (1H-NMR). The curing behaviors of NBen-a and NBen-De were characterized by differential scanning calorimetry (DSC) and FTIR. Thermal stability and dynamic mechanical properties of the cured NBen-a and NBen-De were investigated using thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The cured NBen-a and NBen-De showed glass transition temperature (Tg), the thermal stability improved as compared to the analogous polybenzoxazine without phenylnitrile group. Copyright © 2008 John Wiley & Sons, Ltd. [source] High-performance liquid chromatography/mass spectrometric and proton nuclear magnetic resonance spectroscopic studies of the transacylation and hydrolysis of the acyl glucuronides of a series of phenylacetic acids in buffer and human plasmaRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2010Elin S. Karlsson The use of high-performance liquid chromatography/mass spectrometry (HPLC/MS) and proton nuclear magnetic resonance (1H NMR) spectroscopy for the kinetic analysis of acyl glucuronide (AG) isomerisation and hydrolysis of the 1-,- O -acyl glucuronides (1-,- O -AG) of phenylacetic acid, (R)- and (S)-,-methylphenylacetic acid and ,,,-dimethylphenylacetic acid is described and compared. Each AG was incubated in both aqueous buffer, at pH 7.4, and control human plasma at 37°C. Aliquots of these incubations, taken throughout the reaction time-course, were analysed by HPLC/MS and 1H NMR spectroscopy. In buffer, transacylation reactions predominated, with relatively little hydrolysis to the free aglycone observed. In human plasma incubations the calculated rates of reaction were much faster than for buffer and, in contrast to the observations in buffer, hydrolysis to the free aglycone was a significant contributor to the overall reaction. A diagnostic analytical methodology based on differential mass spectrometric fragmentation of 1-, -O- AGs compared to the 2-, 3- and 4-positional isomers, which enables selective determination of the former, was confirmed and applied. These findings show that HPLC/MS offers a viable alternative to the more commonly used NMR spectroscopic approach for the determination of the transacylation and hydrolysis reactions of these AGs, with the major advantage of having the capability to do so in a complex biological matrix such as plasma. Copyright © 2010 John Wiley & Sons, Ltd. [source] NMR solution structure of a potent cyclic nonapeptide inhibitor of ICAM-1-mediated leukocyte adhesion produced by homologous amino acid substitutionCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2004L.O. Sillerud Abstract:, We have previously described a disulfide-linked cyclic nonapeptide (inhibitory peptide-01, IP01), with the sequence CLLRMRSIC, which binds to intercellular adhesion molecule-1 (ICAM-1), and blocks binding to its counter-structure, the integrin ,L,2 (leukocyte functional antigen-1, LFA-1) (Sillerud et al., J. Peptide Res. 62, 2003: 97). We now report the optimization of this peptide by means of single homologous amino acid substitutions to yield a new peptide (IP02-K6; CLLRMKSAC) which shows an approximately sixfold improvement in inhibitory activity of multivalent leukocyte binding (inhibition constant for 50% inhibition, IC50 = 90 ,m) compared with IP01 (IC50 = 580 ,m). This improvement in activity gives IP02-K6 potent in vivo activity in a murine model of ischemia reperfusion injury (Merchant et al., Am. J. Physiol. Heart Circ. 284, 2003: H1260). In order to determine the structural features relevant to ICAM-1-binding, we have determined the structure of IP02-K6 using proton nuclear magnetic resonance (NMR) spectroscopy and restrained molecular modeling. In our previously reported study of solution models of IP01, we observed three interconverting conformations during low-temperature molecular dynamics simulation. In the present study, we find a single conformation of IP02-K6 similar to one of the previously found conformations of IP01 (family C). In particular, an R4-S7 , -turn is present in similar proportions in both conformation C of IP01 and in IP02-K6; this motif is important in binding to ICAM-1 because this turn enables the IP02-K6 backbone to drape over proline-36 on ICAM-1. The NMR-derived solution model of IP02-K6 was found to dock at the ,L,2 -binding site on ICAM-1 with no changes in peptide backbone conformation. This docking model displaced five of the 15 ,L,2 residues at the ICAM-1-binding site and provided a rationale for understanding the quantitative relationship between IP02-K6 structure and biologic activity. [source] Biochemical changes in selenite cataract model measured by high-resolution MAS 1H NMR spectroscopyACTA OPHTHALMOLOGICA, Issue 5 2006Miroslav Fris Abstract. Purpose:, To correlate certain levels of lens opacification with high-resolution magic-angle spinning proton nuclear magnetic resonance (HR-MAS 1H NMR) spectroscopy analysis of the biochemical changes in rat lenses in a selenite cataract model. Methods:, Selenite cataract was induced by injecting 13-day-old Sprague-Dawley rat pups with a single subcutaneous dose of sodium selenite (3.28 mg/kg in 0.9% sodium chloride solution). Lens opacification was observed using a photographic slit-lamp microscope at selected time-points 3, 6 and 9 days after selenite injection and was then graded (levels 0, 1 and 2). The animals were killed after the slit-lamp microscopy, lenses were removed and HR-MAS 1H NMR spectra from intact lenses were obtained. Relative changes in metabolite concentrations were determined after comparison with matched lenses from untreated animals. Results:, Photographic slit-lamp microscopy revealed different stages of cataract in all animals treated with selenite. In the high quality HR-MAS 1H NMR spectra of the lenses, more than 30 different metabolites were identified in each lens. With the exception of taurine, the concentrations of all amino acids showed a significant increase (p < 0.05) in the second level of cataract. By contrast, glutathione (GSH), succinate and phosphocholine concentrations were significantly reduced. Conclusions:, For the first time, this study demonstrates the potential to correlate the level of lens opacification with the biochemical changes obtained with HR-MAS 1H NMR spectroscopy analysis in a selenite cataract model. [source] Interactions between Brushlike Polyacrylic Acid Side Chains on a Polyacrylate Backbone in Dioxane,WaterCHEMPHYSCHEM, Issue 2 2005Fengjun Hua Dr. Abstract Densely grafted polyacrylic acids (d-PAAs) with overcrowded PAA side chains on the polyacrylate main chains were synthesized and characterized. Acryloyl poly(tert -butyl acrylate) macromonomer [M-P(tert- BA)] was prepared with a definite chain length (n=29) by atom-transfer radical polymerization (ATRP), then homopolymerization was carried out to produce densely grafted P(tert- BA)s with polyacrylate main chains of two different lengths (m=27 and 161). The two d-PAAs were obtained by hydrolyzing d-P(tert- BA)s in the presence of trifluoroacetic acid (TFA). The d-PAAs exhibit intermolecular and intramolecular hydrogen bonding between the carboxylic groups of PAA side chains in dioxane and pyridine; both were investigated using proton nuclear magnetic resonance (1H NMR) spectroscopy. The intermolecular hydrogen bonding was found to be dependent on polymer concentration, temperature, and water content. The intramolecular association between the PAA side chains was found to produce a contraction of the hydrodynamic volume of the d-PAA. Intermolecular hydrogen bonding produces aggregates, as demonstrated by dynamic light scattering (DLS). The clusters were found to shrink as the overall water concentration decreased, and this effect is tentatively explained by considering the gradient in chemical potential of water inside the clusters in comparison with the solvent phase. [source] Synthesis, spectral properties and application of novel disazo disperse dyes derived from polyester wasteCOLORATION TECHNOLOGY, Issue 2 2010V S Palekar Terephthalic dihydrazide was obtained through aminolytic depolymerisation of polyester bottle waste by using hydrazine hydrate. It was further reacted with 4-aminobenzoic acid in the presence of polyphosphoric acid to obtain a cyclic compound, 4,4,-[5,5,-(1,4)-phenylene)bis(1,3,4-oxadiazole-5,2-diyl)dianiline, having a heterocyclic moiety. Diazotisation of this compound followed by coupling with various N,N -disubstituted anilines afford a series of novel disazo disperse dyes. The structures of these synthesised dyes were confirmed by elemental analysis and Fourier Transform,infrared, proton nuclear magnetic resonance and mass spectroscopy. Ultraviolet,visible spectra of these azo dyes in different polar solvents showed considerable variation in the wavelength of maximum absorbance (,max). Application of these dyes on polyester and nylon fabrics using high-temperature dyeing methods gave brilliant yellowish red hues with fair to moderate light fastness and very good to excellent wash fastness and sublimation fastness. [source] | |||||||||||||