Stereochemical elucidation of complex α‐methyl and β‐methylene carbon resonances in poly(2‐hydroxy ethyl methacrylate‐co‐methacrylonitrile) by 2D NMR

Copolymers of 2‐hydroxy ethyl methacrylate and methacrylonitrile (H/M) of different composition were synthesized by free radical bulk polymerization using azobisisobutyronitrile (AIBN) as an initiator under nitrogen atmosphere. The copolymers composition were calculated from ¹H and quantitative ¹³C{¹H}NMR spectra. The complete spectral assignment of complex and overlapped α‐methyl and β‐methylene carbon regions in ¹³C{¹H} NMR spectrum in term of compositional and configurational sequences of H/M copolymers were done with the help of two‐dimensional heteronuclear single quantum coherence (HSQC) and total correlation spectroscopy (TOCSY). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Formation of Polar Compounds During Deep‐frying—Determination by 1H NMR and ESR

The present study aims to elucidate the factors influencing the generation of polar compounds in oils during deep‐frying. Oils with different fatty acid compositions, including palm oil (PO), refined palm kernel oil (RPKO), and refined coconut oil (RCO), are applied in successive frying processes. ¹H NMR spectra reveal that heated PO has a higher percentage of allyl acyl group and is more prone to formation of non‐polar dimeric triglycerides as compared to other types of oils. In addition, electron spin resonance (ESR) spectra indicate that alkyl radicals are more predominant than alkoxy radicals in heated PO. In contrast, RPKO and RCO are inclined to generation of alkoxy radicals during the thermal treatment. The results reveal that oils with high unsaturated fatty acid content are more prone to generation and oxidation of non‐polar dimeric triglycerides. Practical Applications: The change in free radical profile and concentration is one of the indicators of lipid oxidation and polymerization. Alterations in the levels of alkyl and alkoxyl radicals, revealed by ESR, can be used to illustrate the formation of polar compounds in deep‐fried oils with different fatty acid compositions. The percentage of allyl acyl group, revealed by ¹H NMR, can be used to predict the generation of polar compounds. Therefore, this study provides useful information for the development of different methods to reduce polar compound formation in oils during thermal processing depending on the fatty acid composition of different deep‐fried oils.     

Blends of natural rubber and polyurethane latices studied by 1H wideline and 13C MAS solid‐state NMR

¹H wideline and ¹³C magic‐angle spinning NMR have been used to study the morphology and dynamics of latex‐cast and solution‐cast film blends of natural rubber (NR) and a polyurethane (PU) based on poly(?‐caprolactone) diol and isophorone di‐isocyanate. ¹H T₁ and T_1ρ relaxation times have been measured, and the extent of interpenetration of the NR and PU constituents has been monitored using the Goldman–Shen technique. The NMR spectra and relaxation properties indicated that the NR and PI constituents largely occupy separated domains on a distance scale of >10 nm. The Goldman–Shen experiments indicated that there was slightly greater contact between NR and PU in the solution‐cast samples than in the latex‐cast. The tensile properties of the films have been measured. The tensile strength and initial Young's modulus pass through a maximum at a PU content of about 50 wt%. © 2002 Society of Chemical Industry     

Determination of the fatty acid profile by 1H‐NMR spectroscopy

The common unsaturated fatty acids present in many vegetable oils (oleic, linoleic and linolenic acids) can be quantitated by ¹H‐nuclear magnetic resonance spectroscopy (¹H‐NMR). A key feature is that the signals of the terminal methyl group of linolenic acid are shifted downfield from the corresponding signals in the other fatty acids, permitting their separate integration and quantitation of linolenic acid. Then, using the integration values of the signals of the allylic and bis‐allylic protons, oleic and linoleic acids can be quantitated. The procedure was verified for mixtures of triacylglycerols (vegetable oils) and methyl esters of oleic, linoleic and linolenic acids as well as palmitic and stearic acids. Generally, the NMR (400 MHz) results were in good agreement with gas chromatographic (GC) analyses. As the present ¹H‐NMR‐based procedure can be applied to neat vegetable oils, the preparation of derivatives for GC would be unnecessary. The present method is extended to quantitating saturated (palmitic and stearic) acids, although in this case the results deviate more strongly from actual values and GC analyses. Alternatives to the iodine value (allylic position equivalents and bis‐allylic position equivalents) can be derived directly from the integration values of the allylic and bis‐allylic protons.     

Kinetic study of radical polymerization. VII. Investigation into the solution copolymerization of acrylonitrile and itaconic acid by real‐time 1H NMR spectroscopy

Free radical solution copolymerization of acrylonitrile (AN) and itaconic acid (IA) was performed with DMSO‐d₆ as the solvent and 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. Weight ratio of the monomers to solvent and molar ratio of initiator to monomers were constant in all experiments. The initial comonomer composition was the only variable in this study. On‐line ¹H NMR spectroscopy was applied to follow individual monomer conversion. Mole fraction of AN and IA in the reaction mixture (f) and in the copolymer chain (F) were measured with progress of the copolymerization reaction. Overall monomer conversion versus time and also compositions of monomer mixture and copolymer as a function of overall monomer conversion were calculated from the data of individual monomer conversion versus time. Total rate constant for the copolymerization reaction was calculated by using the overall monomer conversion versus time data and then k_p/k_t^0.5 was estimated. The dependency of k_p/k_t^0.5 on IA concentration was studied and it was found that this ratio decreases by increasing the mole fraction of IA in the initial feed. The variation of comonomer and copolymer compositions as a function of overall monomer conversion was calculated theoretically by the terminal model equations and compared with the experimental data. Instantaneous copolymer composition curve showed the formation of alternating copolymer chain during copolymerization reaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3253–3260, 2007     

Assignment of 1H NMR spectrum and investigation of oxidative degradation of poly(ethylenimine) using 1H and 13C 1‐D and 2‐D NMR

The ¹H NMR spectrum of poly(ethylenimine) (PEI) has been assigned using two‐dimensional NMR correlation with the previously established assignment of the ¹³C spectrum. The oxidative thermal and UV degradation of PEI has been studied using mass loss measurements, and NMR and Fourier transform infrared spectroscopy. Analysis of the spectra of the degradation products shows that the degradation process may readily be monitored, particularly by ¹³C NMR. The major products are formamide and other amide groups which may be understood in terms of chain scission and dehydration reactions of hydroperoxides. Copyright © 2006 Society of Chemical Industry     

Study of propylene‐1‐butene‐ethylene terpolymer and reactor blend by TREF and 13C‐NMR

A terpolymer of propylene‐1‐butene‐ethylene (TERPO) and a reactor mixture of TERPO with an ethylene‐1‐butene copolymer (BLEND) were completely characterized by TREF, ¹³C‐NMR, DSC, and GPC, from which special equations for quantitative ¹³C‐NMR were derived. TERPO was shown to be composed mainly of highly isotactic propene and similar amounts of ethylene and 1‐butene. BLEND fractions were composed of variable amounts of TERPO and a random copolymer of ethylene‐1‐butene. The blend of TERPO and copolymer acts as two independent phases, each having its own elution temperatures dependent only on its crystallizability, itself only influenced by the comonomer content. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1880–1890, 2001     

Hydrosoluble copolymers of acrylamide‐(2‐acrylamido‐2‐methylpropanesulfonic acid). Synthesis and characterization by spectroscopy and viscometry

Hydrosoluble copolymers containing sulfonic acid groups incorporated into a macromolecule were synthesized. The group of polymers studied was obtained by free radical solution polymerization, using potassium persulfate as an initiator. The copolymerization of the monomers 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) and acrylamide (AA) was carried out at different pH values of the reaction medium of the monomer mix. The copolymers were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR) and Fourier transform infrared spectroscopy (FTIR). The viscosity behavior of the copolymers in NaCl solution showed a dependency on the pH of the reaction medium, with higher pH leading to lower viscosities. The acidic conditions of this medium affect the initiator decomposition rate, which is a probable cause of the viscosity variation, and the extent of decomposition increases with increasing pH. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 192–198, 2003     

1H T2‐NMR monitoring of crosslinked polyolefin aging

This work examines the correlation between the ¹H‐NMR T₂ relaxation constant and the mechanical properties of aged crosslinked polyolefin cable insulation. T₂ experiments on unswollen samples could not differentiate between unaged and highly aged materials; all exhibited ¹H T₂ constants of approximately 0.5 ms. To accentuate the effects of aging, samples were swollen in various solvents. Unaged samples had T₂ values of approximately 15 ms in good solvents. With thermal aging, T₂ values decreased as the ultimate tensile elongation decreased. However, the correlation between T₂ and elongation differed for samples irradiated with high‐energy radiation and for materials aged above versus below the crystalline melting temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2578–2582, 2003     

Evaluation of the diethylene glycol bis(allyl carbonate)/acrylic acid copolymer behavior by solid‐state 13C‐NMR

The dynamic behavior of diethylene glycol bis(allyl carbonate) (CR‐39)/acrylic acid (AA) copolymers was evaluated by ¹³C high‐resolution solid‐state nuclear magnetic resonance (NMR). The NMR data showed that the copolymerization of CR‐39 and AA generated copolymers with different molecular behaviors as a function of AA content, which promoted changes in the crosslinking of CR‐39 chains and in the intramolecular forces. The copolymerization process influenced the sequence distribution and domain formation of the monomers, which is a consequence of the dispersion of comonomers along the macromolecular chains. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 740–745, 2005     

Effect of crystallization on microstructure and mechanical properties of poly[(ethylene oxide)‐block‐(amide‐12)]‐toughened poly(lactic acid) blend

The effect of crystallization on the microstructure and mechanical properties of a poly[(ethylene oxide)‐block‐(amide‐12)] (PEBA)‐toughened poly(lactic acid) (PLA) blend was investigated. Annealing was used to govern the crystallization microstructure and hence the mechanical properties of the blend. Crystallization resulted in the morphology of the PLA component altering from a continuous amorphous phase to continuous crystalline phase. Moreover, as the crystallization of PLA proceeded, the degree of crystallinity, spherulite size and lamellar thickness increased, and the interlamellar and interspherulitic connections became weaker. These led to the large plastic deformation in the matrix during tension being suppressed, and cracks appeared easily under tensile load, which was favorable to fracture for the blend during tension and so a small elongation at break was obtained. However, the elongation at break for all the annealed specimens was higher than that for neat amorphous PLA, suggesting that PEBA still showed a toughening effect for PLA under annealing. © 2012 Society of Chemical Industry     

The curing of UF resins studied by low‐resolution 1H‐NMR

A series of UF resins and one MUF resin were studied by low‐resolution ¹H‐NMR. The mobility of the resin during curing could be followed by measuring the spin‐spin relaxation time (T₂) with curing time. The relative curing behavior was similar to that found by traditional gel time measurements. In addition, extra features in the T₂ plots with curing time showed at what point the bulk of the condensation reactions took place. The speed of cure was also related to the chemical groups in the liquid resin, and it was found that the linear methylol groups were mainly responsible for the curing speed of the resins. By studying the curing with different hardener levels and glue concentrations it was found that a UF resin is more sensitive to the glue mix concentration than an MUF resin. A cured resin was also studied after curing to investigate postcuring effects. Water seemed to play the biggest role in the postcure, with substantial amounts present immediately after cure, which decreased with curing time and aging. For the low mol ratio resins studied here further curing reactions did not seem to play a major role in the post curing phenomenon. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 754–765, 2000     

A study of the products and mechanism of the thermal oxidative degradation of poly(ethylene oxide) using 1H and 13C 1‐D and 2‐D NMR

The products and mechanism of the thermal oxidative degradation of poly(ethylene oxide) at 150 °C have been analysed using ¹H and ¹³C 1‐D and 2‐D NMR spectroscopy, including COSY, HMQC, HMBC and DOSY techniques. Peaks from methanoate ester chain ends (in the majority), in‐chain esters, peroxy groups, acetal links and ethanoyl chain ends have been assigned. Two small molecule degradation products, 2‐hydroxyethyl methanoate and ethylene glycol dimethanoate have been identified. Copyright © 2004 Society of Chemical Industry     

Evaluation of EVA–PVAc blend behavior by 1‐D and 2‐D solid‐state NMR

Ethylene‐co‐vinyl acetate and poly(vinyl acetate) blends were prepared in different proportions by melting in a HAAKE Rheomix mixer. The blends were prepared at a fixed temperature, rotation rate, and processing time. High‐resolution solid‐state nuclear magnetic resonance was chosen to characterize the blends with respect to structure–mobility–compatibility employing magic angle spinning with cross polarization and high‐power hydrogen decoupling and the measurements of the proton spin–lattice relaxation time in the rotating frame (Tρ). The miscibility between polymer chains was also studied by two‐dimensional ¹H–¹³C shift correlation (HETCOR). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 221–226, 1999     

Thermal oxidative and photo‐oxidative degradation of polytetrahydrofuran studied using 1H NMR, 13C NMR and GPC

The products and mechanism of the thermal oxidative degradation at 180 °C and the photo‐oxidative degradation at 40 °C of polytetrahydrofuran have been investigated using ¹H NMR, ¹³C NMR and GPC. The NMR analysis was assisted by the use of DEPT ¹³C spectra, two‐dimensional NMR spectroscopy (COSY, HMQC and HMBC) and chemical shift simulation software. The NMR spectra of both thermally and photolytically degraded samples were similar showing that the degradation mechanisms were similar. GPC indicated that both chain scission, leading to lower molar mass products, and chain extension, leading to higher molar mass products, occurred initially. NMR analysis of the initial soluble degraded polymers showed that chain scission resulted in formate, aldehyde, propyl ether, butyl ether and propanoyl chain ends, and in‐chain ester groups were also formed. For longer periods of degradation, crosslinked gels were formed but these were not amenable to detailed structural characterisation by high‐resolution NMR to determine the crosslink mechanism. Copyright © 2004 Society of Chemical Industry     

Graft copolymerization of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid onto carboxymethylcellulose (sodium salt) by H2O2/Fe+2 redox pair

The effect of the reaction conditions on the grafting parameters during grafting of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid onto sodium carboxymethylcellulose using H₂O₂/Fe⁺² redox pair are studied at 30°C. The grafting ratio, add on, and conversion initially increase with the H₂O₂ concentration in the range of (10.0–15.0) × 10^?2 mol dm^?3. Thereafter, these parameters decrease with the H₂O₂ concentration. The grafting ratio, add on, and conversion increase when increasing the ferrous ion concentration from (0.5 to 4.0) × 10^?2 mol dm^?3 and decrease with a further increase in the concentration. It is observed that the grafting ratio and add on increase with the monomer concentration, whereas the conversion decrease. The hydrogen ions seem to be facilitating the grafting reaction up to a certain concentration and after this concentration seem to be retarding the process. The grafting ratio, add on, and conversion decrease with the sodium carboxymethylcellulose concentration. When increasing the time period from 60 to 90 min, the grafting parameters increase but decrease thereafter. Similarly, when increasing the temperature from 25 to 30°C, the grafting parameters increase and decrease thereafter. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4819–4825, 2006     

Degradation of 1‐amino‐4‐bromoanthraquinone‐2‐sulfonic acid using combined airlift bioreactor and TiO2‐photocatalytic ozonation

BACKGROUND: Traditional treatment systems failed to achieve efficient degradation of anthraquinone dye intermediates at high loading. Thus, an airlift internal loop reactor (AILR) in combination with the TiO₂‐photocatalytic ozonation (TiO₂/UV/O₃) process was investigated for the degradaton of 1‐amino‐ 4‐bromoanthraquinone‐2‐ sulfonic acid (ABAS). RESULTS: The AILR using Sphingomonas xenophaga as inoculum and granular activated carbon (GAC) as biocarrier, could run steadily for 4 months at 1000 mg L^?1 of the influent ABAS. The efficiencies of ABAS decolorization and chemical oxygen demand (COD) removal in AILR reached about 90% and 50% in 12 h, respectively. However, when the influent ABAS concentration was further increased, a yellow intermediate with maximum absorbance at 447 nm appeared in AILR, resulting in the decrease of the decolorization and COD removal efficiencies. Advanced treatment of AILR effluent indicated that TiO₂/UV/O₃ process more significantly improved the mineralization rate of ABAS bio‐decolorization products with over 90% TOC removal efficiency, compared with O₃, TiO₂/UV and UV/O₃ processes. Furthermore, the release efficiencies of Br^? and SO₄^2? could reach 84.5% and 80.2% during TiO₂/UV/O₃ treatment, respectively, when 91.5% TOC removal was achieved in 2 h. CONCLUSION: The combination of AILR and TiO₂/UV/O₃ was an economic and efficient system for the treatment of ABAS wastewater. © 2012 Society of Chemical Industry     

Carbon‐13 NMR,GPC, and DSC study on a propylene‐1‐butene copolymer fractionated by temperature rising elution fractionation

A random copolymer of propylene with small amounts of 1‐butene comonomer, synthesized with a Ziegler–Natta catalyst, was fractionated by temperature rising elution fractionation (TREF) to systemically investigate the fraction samples' molecular microstructure, as well as their relationship to the melting and crystallization behavior. First, TREF was employed to fractionate the sample, and then crystallization analysis fractionation (Crystaf) was used to check the effect of the TREF experiment. In the characterization of the molecular microstructure, carbon‐13 NMR spectroscopy (¹³C NMR) and gel permeation chromatography (GPC) experiments gave the following results: the fraction samples have relatively uniform molecular microstructure; with an increase in elution temperature, the 1‐butene content in the fraction samples decreases, but the molecular weight (M_n) and number average sequence length of propylene (n?_P) increase. In the study on melting and crystallization behavior, differential scanning calorimetry (DSC) experimental results show that the melting temperature increasingly decreases with an increase in 1‐butene content; however, dependence of the melting temperature on molecular weight becomes weaker and weaker with an increase in the number average molecular weight in the range of number average molecular weight below 1.82 × 10⁵ g/mol. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 845–851, 2006