Study on the spin probe‐added polymeric dense membranes by 13C solid‐state nuclear magnetic resonance spectroscopy

This article is a duplicate of an article previously published in the Journal of Applied Polymer Science, Vol. 99, No. 6, March 15, 2006, pp. 3062‐3069 http://doi.wiley.com/10.1002/app.22908 . We regret any inconvenience this may have caused.     

Radiation degradation of epoxidized natural rubber studied by solid‐state nuclear magnetic resonance and infrared spectroscopy

The mechanism of radiation‐induced structural changes in epoxidized natural rubber was investigated using nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. Samples were irradiated both under vacuum and in air. Because the rubbers crosslinked during irradiation, solid‐state NMR had to be used. The cross polarized/magic angle spinning NMR spectra were used to calculate the radiation yields. Ring opening of the epoxy groups was found to occur during irradiation. Most of the crosslinking was due to epoxy group ring opening, and very little or no C C crosslinking was observed. © 2000 Society of Chemical Industry     

The composition of hydrogenated fats by high-resolution13C nuclear magnetic resonance spectroscopy

The high-resolution¹³C nuclear magnetic resonance spectra of twelve hydrogenated fats have been examined. Each spectrum contains 50–100 signals and reveals much about the nature of the acyl chains of both double-bond position and configuration. The signals for the ω1, ω2 and ω3 carbon atoms give information on thecis andtrans isomers of the Δ15, Δ14, Δ13 and Δ12 18:1 esters, respectively. Allylic signals distinguish betweencis andtrans esters, and the proportion of totalcis to totaltrans isomers can be obtained from these. Olefinic signals are the most informative, and most of these have been assigned. This leads to a semi-quantitative estimate of the various 18:1 isomers present. Assignments are based mainly on information already in the literature, but some were confirmed after urea fractionation of the acids from a hydrogenated oil in whichcis andtrans monoene acids were separately concentrated.     

Value‐added bioconversion of biomass by solid‐state fermentation

The value‐added bioconversion of biomass is necessary due to the depletion of fossil fuels and deterioration of the global environment situation. Based on the analysis of characteristics of solid materials and the applicability of solid agro‐industrial residues used as feedstock for solid‐state fermentation (SSF), the authors established a value‐added bioconversion system for biomass using the key technology SSF. This article gives an overview of biomass bioconversion by SSF and the corresponding advances achieved in recent years. Copyright © 2012 Society of Chemical Industry     

Microstructure of solution-chlorinated polyethylene by 13C nuclear magnetic resonance

Solution-chlorinated polyethylene prepared by a modified method has been characterized using ¹³C nuclear magnetic resonance (n.m.r.) and differential thermal analysis (d.t.a.). The results show that the residual paraffin segments, melting point and crystallinity decrease rapidly with increasing chlorine content. The prepared polymer seems to have a homogeneous chlorine distribution.     

Chain conformation of polyethylene in the solid state as studied by 13C cross-polarization/magic angle spinning nuclear magnetic resonance spectroscopy

High-resolution ¹³C nuclear magnetic resonance (n.m.r.) spectra of melt-quenched polyethylene and polyethylene single crystals are measured by the cross-polarization/magic angle spinning technique. Melt-quenched polyethylene and polyethylene single crystals have four small upfield peaks, a shoulder on the main peak and three small peaks, respectively. Based on the ¹³C n.m.r. resonance lines of cyclic paraffin C₆₄H₁₂₈ reported previously, it is concluded that the main peak and the three upfield peaks arise from the trans zigzag structure region and the folded structure region, respectively. From these peak intensities, it is estimated that the stem length of polyethylene single crystals is approximately 125 Å. Taking into account an error in the estimation of the small peak intensities, the calculated stem length of 125 Å is consistent with the crystal thickness (120–150 Å) observed directly by electron microscopy. It can be concluded, therefore, that polyethylene single crystals mainly contain sharply folded structure. Melt-quenched polyethylene may contain sharply folded structure to some extent in addition to loose loops.     

Determination of iodine value of palm and palmkernel oil by carbon‐13 nuclear magnetic resonance spectroscopy

High resolution carbon‐13 nuclear magnetic resonance ( ¹³ CNMR) can be used for characterization of palm oil and palmkernel oil in determining the iodine value (IV) of the oil. It is only necessary to obtain the quantitative ¹³ CNMR spectrum of the oil in dilute CDCl₃ solution in the region of δ30.0‐δ24.7 ppm, which pertains to the methylene carbons along the acyl chain from the β‐carbonyl to the ω‐4. From the peak areas in the spectrum the average number of double bonds per triacylglycerol molecule and the average molecular weight can be calculated and hence the IV. The IVs of 18 samples of palm and palmkernel oil have been determined by ¹³ CNMR and by the Official Method of the American Oil Chemists Society. There is good agreement between the two sets of IVs. Conditions for obtaining reliable IVs by this ¹³ CNMR method are given.     

Solid state 13C nuclear magnetic resonance of heavy oil/bitumen-derived solids

Solid state ¹³C n.m.r. analysis of the insoluble organic matter associated with the clay mineral, silica, and heavy metal minerals of heavy oils/bitumen is reported. The conditions under which these measurements can be made are related to the concentration of organic matter found, the nature and amount of paramagnetic constituents, and contact times. The data are related to changes in hydrophilic/hydrophobic surface properties of the solids. The relationship with bitumen losses in recovery processes is also discussed.     

Analysis of the conjugated trienoic acid containing oil fromFevillea trilobata by13C nuclear magnetic resonance spectroscopy

Oil ofFevillea trilobata has the composition palmitic acid 31%, stearic acid 12%, oleic acid 11%, linoleic acid 7%,cis,trans,cis 9,11,13-octadecatrienoic acid 30% andcis,trans,trans-9,11,13-octadecatrienoic acid 9%. The oil was analyzed and components identified by¹³C NMR spectroscopy; the composition was also confirmed by conventional methods. Assignment of¹³C NMR signals of conjugated trienoic acids is discussed and it is shown that mixtures of isomeric conjugated acids can be analyzed by this method. NRCC No. 17797.     

Oxidation in fish lipids during thermal stress as studied by 13C nuclear magnetic resonance spectroscopy

¹³C Nuclear magnetic resonance spectroscopy has been applied to elucidate the mechanism of lipid oxidation occurring during thermal treatment of fish. Effects of temperature and time of processing have been studied by means of a model system of lipids, extracted from salmon (Salmo salar) muscle, to simulate industrial conditions of canning. Unsaturated fatty acids located at the sn-2 position of the glycerol moiety were the most prone to oxidative damage. Regarding the mechanism of the reaction, results inferred from olefinic and methylenic resonances indicated a higher susceptibility of the allylic sites closest to the carbonyl group, followed by those placed near the methyl terminal group. Unsaturations located in the middle of the carbon chain did not show much damage. The glyceryl region provided an unusual resonance at 53.4 ppm, which could be assigned to a hydroxylic compound formed during process.     

Microstructure study of styrene/n-butyl acrylate emulsion copolymers by 13C nuclear magnetic resonance spectroscopy

A detailed study of the sequence distribution in styrene (S)/n-butyl acrylate (A) emulsion copolymers using ¹³C nuclear magnetic resonance spectroscopy is reported. From the interpretation of the spectra of the homopolymers and copolymers, assignment of the carbonyl (A) and quaternary (S) carbon atom resonances has been made. This provides a quantitative estimation of the compositional triad distributions in the copolymers. The results were found to be in relatively good agreement with calculated triad fractions deduced from a simulation program taking into account the actual reactivity ratios and type of emulsion process.     

Structural characterization by 13C nuclear magnetic resonance of hydrolysed carboxymethylcellulose

Summary In order to characterize heavyweight carboxymethylcellulose (C.M.C) by ¹³C NMR it is necessary to hydrolysis them. This paper proposes and compares three different ways of degradation: acidic hydrolysis, sonication and enzymatic degradation. Acidic hydrolysis leads to poor results due to a strong alteration of the sample. Sonication gives quite good results but the enzymatic degradation is the most efficient method for degrading C.M.C under good conditions.After hydrolysis, the sample was analysed by ¹³C NMR and HPLC to obtain structural information such as substitution degree, preferential substitution sites and regularity of the substitution along the polymeric chain.     

Quantitative determination of castor oil in edible and heat-abused oils by13C nuclear magnetic resonance spectroscopy

Application of¹³C nuclear magnetic resonance (NMR) spectroscopy for detection of castor oil (CO) in various edible oils, such as coconut oil, palm oil, groundnut oil and mustard oil, is described. Characteristic signals observed at δ 132.4, δ 125.6, δ 71.3, δ 36.8 and δ 35.4 ppm, due to C10, C9, C12, C13 and C11 carbons of ricinoleic acid (RA) in CO, were selected for distinguishing it from edible oils. Quantitative¹³C NMR spectra of oils were recorded in CDCl₃ with a gated decoupling technique. The minimum detection limits for qualitative and quantitative analyses were 2.0 and 3.0%, respectively. The proposed method is simple, nondestructive and requires no sample pretreatment. Its application to heat-abused oils has also been demonstrated successfully without any of the interferences observed in most other methods.     

The study of natural epoxy oils and epoxidized vegetable oils by13C nuclear magnetic resonance spectroscopy

The¹³C nuclear magnetic resonance spectra ofVernonia galamensis seed oil and of epoxidized palm super olein, soybean oil and linseed oil have been recorded and interpreted. The chemical shifts of the major signals are assigned and semi-quantitative results are derived. The spectroscopic procedure provides a useful method of analyzing oils that contain epoxy acids. The epoxide function differs from a double bond in its influence on the chemical shifts of nearby carbon atoms.     

Detection of lead ion binding on bifunctional chelating/ion‐exchange resins by cross‐polarization/magic‐angle spinning solid‐state nuclear magnetic resonance

Solid‐state nuclear magnetic resonance (S‐NMR) can reveal much useful information, including conformations, stereoregularity, defect structures, and comonomer sequence. S‐NMR is especially useful for revealing microstructural differences that can alter local polymer chains. A series of bifunctional chelating/ion‐exchange resins, containing differing ratios of iminodiacetic acid to acetic acid, were synthesized. Cross‐polarization magic‐angle spinning (CP/MAS) ¹³C‐NMR was employed to measure conformation changes both before and after the bonding of ligands and lead ion adsorbed on bifunctional chelated/ion‐exchange resins in this investigation. From the ¹³C‐NMR spectra, as the lead ion was adsorbed by the iminodiacetic acid chelating group, the motion of molecular chain would be inhibited and the resonance peaks of the carboxylate anion at 170 ppm would shift downfield. Compared to the FTIR results, the downfield shift of the resonance peaks indicated that the bonding of carboxylate anion and lead ion adsorbed displayed an ionic trend. Furthermore, the bonding of the carboxylic group and lead ion adsorbed changed from ionic to covalent as the chelating group in bifunctional/ion‐exchange resins decreased. The linear relationship between the areas of those resonance peaks and the amount of lead ion adsorbed was obtained from the spectra fitting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 919–928, 2002     

Use of high-resolution 13C nuclear magnetic resonance spectroscopy for the screening of virgin olive oils

¹³C Nuclear magnetic resonance (NMR) spectra of 104 oil samples were obtained and analyzed in order to study the use of this technique for routine screening of virgin olive oils. The oils studied included the following: virgin olive oils from different cultivars and regions of Europe and north Africa, and refined olive, “lampante” olive, refined olive pomace, high-oleic sunflower, hazelnut, sunflower, corn, soybean, rapeseed, grapeseed, and peanut oils, as well as mixtures of virgin olive oils from different geographical origins and mixtures of 5–50% hazelnut oil in virgin olive oil. The analysis of the spectra allowed us to distinguish among virgin olive oils, oils with a high content of oleic acid, and oils with a high content of linoleic acid, by using stepwise discriminant analysis. This parametric method gave 97.1% correct validated classifications for the oils. In addition, it classified correctly all the hazelnut oil samples and the mixtures of hazelnut oil in virgin olive oil assayed. All of these results suggested that ¹³C NMR may be used satisfactorily for discriminating some specific groups of oils, but to obtain 100% correct classifications for the different oils and mixtures, more information than that obtained from the direct spectra of the oils is needed.     

13C solid‐state NMR analysis of the DGEBA/TETA epoxy system

Mechanical properties measurements, like Charpy impact tests, provided evidence that the macromolecular network of the epoxy system formed by the hexafunctional triethylene tetramine hardener, TETA, with the diglycidyl ether of bisphenol A monomer, DGEBA, can be modified by changing the hardener content. The previously analyzed monomer‐to‐hardener ratios were here studied by ¹³C‐NMR solid state techniques. The results from crosspolarization/magic angle spinning (CPMAS) ¹³C‐NMR spectra, together with the evaluation of proton spin‐lattice relaxation time in the rotating frame (Tρ), display the behavior of these epoxy/hardener mixtures considering the mobility and interaction of molecular segments present at the macromolecular structure. The results also show that the epoxy‐rich mixtures form tight, and therefore brittle, structures as previously observed by mechanical tests. The stoichiometric monomer‐to‐hardener ratio is a transition point where an increase in the mobility was found. For the amine‐rich mixtures the obtained results suggest the presence of domains with different segmental mobilities. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2358–2362, 2000     

Hypothetical average structures of two coal liquid asphaltenes from solid state 13 C nuclear magnetic resonance and 1 H nuclear magnetic resonance data

The hypothetical average structures of two coal liquid asphaltenes were determined using solid state 13 C NMR and 1 H NMR data. From the 1 H NMR data average molecular structural parameters were obtained using the Brown-Ladner method to get a general average structure. From the solid state 13 C NMR data, estimations of percentages of tertiary and quaternary aromatic carbons and secondary/tertiary and primary/quaternary aliphatic carbons were made. The hypothetical average molecules obtained agreed closely with experimental results.