High‐resolution carbon‐13 nuclear magnetic resonance study of natural resins

Developing a methodology of analysis for the identification of the components presented in natural resins without a previous isolation or treatment, we first chose to use liquid nuclear magnetic resonance(NMR) to assign the main components. However, solid‐state NMR techniques give much more information about the chemical components presents in the resins than solution NMR, so we changed the methodology. The first approach must be the application of solid‐state NMR techniques and continuation of the identification process by analysis of the data obtained. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1848–1854, 2002     

Solid‐state 13C‐NMR and study of the subproducts obtained from corn industry

The two types of commercial corn flour subproducts from the Brazilian corn industry containing starch with low fat and with fat were investigated by solid‐state NMR techniques to improve their uses. From the NMR techniques used, it was characterized that after a treatment the quantity of fibers decreased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1680–1685, 2002; DOI 10.1002/app.10547     

Solid‐state carbon‐13 NMR study of material composites based on sugarcane bagasse and thermoplastics polymers

The composites formed by sugarcane bagasse and thermoplastic polymers, such as polypropylene (PP), polyethylene (PE), and ethylene‐co‐vinyl acetate (EVA), have been analysed by carbon‐13 high‐resolution solid‐state nuclear magnetic resonance (NMR), employing crosspolarization magic angle spinning (CPMAS); variable contact‐time experiment and proton spin‐lattice relaxation time in the rotating frame. NMR responses showed that these techniques can be used to observe the degree of compatibility and homogeneity of different polymers composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2150–2154, 2001     

13C‐NMR study on cure‐accelerated phenol–formaldehyde resins with carbonates

Both liquid‐ and solid‐state ¹³C‐NMR spectroscopies were employed to investigate the cure‐acceleration effects of three carbonates [propylene carbonate (PC), sodium carbonate (NC), and potassium carbonate (KC)] on liquid and cured phenol–formaldehyde (PF) resins. The liquid‐phase ¹³C‐NMR spectra showed that the cure‐acceleration mechanism in the PC‐added PF resin seemed to be involved in increasing reactivity of the phenol rings, while the addition of both NC and KC into PF resin apparently resulted in the presence of ortho–ortho methylene linkages. Proton spin‐lattice rotating frame relaxation time (T_1ρH) measured by solid‐state ¹³C‐CP/MAS‐NMR spectroscopy was smaller for the cure‐accelerated PF resins than for that of the control PF resin. The result indicated that cure‐accelerated PF resins are less rigid than the control PF resin. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 841–851, 2000     

High‐resolution carbon nuclear magnetic resonance study of styrene/α‐methylstyrene/acrylonitrile terpolymers

Terpolymers formed from styrene, α‐methylstyrene (AMS), and acrylonitrile (AN) were prepared in different proportions. According to the reaction conditions, the terpolymers presented random sequence distributions. AMS, because of steric hindrance, presented a high degree of instability, which promoted depolymerization. AN promoted a long insertion of AMS monomers, which caused an acceleration of the propagation reaction. This also caused a depolymerization process. With ¹³C‐NMR solution analysis, it was possible to detect the depolymerization process. With solid‐state NMR results, it was demonstrated that AMS constituted the highest mobility domain. Finally, the values determined for the proton spin–lattice relaxation time in the rotating frame confirmed that the prepared terpolymers were random, but a homogeneous monomer distribution sequence was also observed from this parameter. © 2003 Wley Periodicals, Inc. J Appl Polym Sci 88: 1004–1009, 2003     

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.     

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     

1H‐ and 13C‐NMR analyses of aqueous polyamideamine–epichlorohydrin resin solutions

More accurate signal assignment for ¹H‐ and ¹³C‐NMR spectra of aqueous solutions of polyamideamine‐epichlorohydrin (PAE) resin and its related compounds was achieved by using distortionless enhancement of polarization transfer (DEPT) and C‐H correlation spectroscopy (COSY) methods. On the basis of the assignment, we developed new methods to determine the content of four‐membered azetidinium ring (AZR) and number‐average degree of polymerization (DP_n) of the repeating unit of PAE by using NMR. Degree of introduction of epichlorohydrin into polyamideamine chains at the initial stage was 75–80%, and the resultant AZR content per one repeating unit in the PAE sample prepared in this study was about 72%. DP_n of the initial polyamideamine was 32, and this value decreased to about 18 during the PAE preparation process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1847–1854, 2004     

Castor‐acrylated monomer 1H‐ and 13C‐nuclear magnetic resonance spectral assignments

Castor‐acrylated monomer (CAM) NMR spectral assignments were made utilizing one‐ and two‐dimensional NMR techniques. The unique structure of CAM resulted in several novel chemical environments which were observed in the NMR spectra. Previously published vegetable oil and fatty acid ester NMR peak assignments were insufficient for complete identification of NMR peaks. Definitive peak assignments, particularly in the alkyl and alkene regions, are required for evaluation of CAM as a specialty comonomer in the synthesis of latex polymers for use as waterborne‐coating binders. The NMR peak assignments for CAM will allow the subsequent evaluation of the copolymerizability of CAM as well as the determination as to whether unsaturation is preserved during latex polymer synthesis. ¹H‐ and ¹³C‐NMR spectra of CAM are provided with supporting evidence for the peak assignments and discussion of their relevance. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1850–1854, 2001     

13C‐NMR study on cure‐accelerated phenol‐formaldehyde resins with carbonates

Both liquid‐ and solid‐state carbon‐13–nuclear magnetic resonance (¹³C‐NMR) spectroscopies were used to investigate the cure acceleration effects of three carbonates (propylene carbonate, sodium carbonate, and potassium carbonate) on liquid and cured phenol‐formaldehyde (PF) resins. The liquid‐phase ¹³C‐NMR spectra showed that the cure acceleration mechanism in the propylene carbonate‐added PF resin seemed to be involved in increasing reactivity of the phenol rings, whereas the addition of both sodium carbonate and potassium carbonate into PF resin apparently resulted in the presence of ortho–ortho methylene linkages. Proton spin‐lattice rotating frame relaxation time (T_1ρH) measured by solid‐state ¹³C cross polarization/magic‐angle spinning NMR spectroscopy was smaller for the cure‐accelerated PF resins than that of the control PF resin. The result indicated that the cure‐accelerated PF resins are less rigid than the control PF resin. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1284–1293, 2000     

The compatibility study of polycarbonate-polyvinyl pyrrolidone blend using high-resolution solid-state nuclear magnetic resonance

The combining nuclear magnetic resonance techniques in the solid state permit the evaluation of the polymeric systems homogeneity. In the polycarbonate-poly(vinyl pyrrolidone) (PVP) blends, the response of proton spin-lattice relaxation time in the rotating frame was the determinant to obtain information on the transition when the quantity of PVP is close to 40% by weight and a better organization of amorphous phase was detected. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 449–453, 1998     

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     

High‐resolution solid‐state NMR investigation of the filler–rubber interaction: 2. High‐speed [1H] magic‐angle spinning NMR spectroscopy in carbon‐black‐filled polybutadiene

This work investigates the behaviour of elastomeric chains (polybutadienes of identical molecular weight but different microstructures) in the close vicinity of carbon black surfaces in order to attain a better understanding of the structure and properties of interphases. Elastomer–filler interactions are assessed through the study of the thermal properties and NMR relaxation characteristics of the corresponding materials. Three series of samples were compared: pure polymers, raw polymer–filler blends (filler loading ratio: 50 phr) and solvent‐extracted blends (so as to get rid of any polymer which is not under the influence of the solid surface). While differential scanning calorimetry points to the existence of an elastomer fraction which is not detected as undergoing the glass transition, ie is strongly immobilized, [¹H] high‐resolution high‐speed magic‐angle spinning solid‐state NMR provides information on the effect exerted by polymer–filler interactions on the mobility of the various constitutive species of the macromolecular backbone. A systematic study of the evolution of the spectral lines yielded by the samples indicates that 1,2‐polybutadiene moieties have a particular affinity towards the carbon black surface which suggests the occurrence of specific interactions at the elastomer–filler interface. © 2001 Society of Chemical Industry     

An investigation of 1H and 13C longitudinal relaxation and relaxation in the rotating frame in solid poly(N‐vinylcarbazole)

¹H and ¹³C longitudinal relaxation times (T₁) and relaxation times in the rotating frame (T_1ρ) have been measured for poly(N‐vinylcarbazole) in the solid state in air and nitrogen atmospheres in an attempt to elucidate molecular motions. In air, the T₁ relaxation of both ¹H and ¹³C was dominated by interaction with absorbed paramagnetic oxygen. In nitrogen, the ¹³C T₁ relaxation times were long (>300 s) and were averaged by ¹³C–¹³C spin diffusion. The ¹³C T_1ρ relaxation times showed an exponential dependence on the strength of the rotating ¹³C magnetic field and were thus controlled by spin–spin processes rather than spin–lattice processes. © 2001 Society of Chemical Industry     

Carbon‐13 nuclear magnetic resonance investigation of styrene–α‐methylstyrene copolymers

A copolymer based on α‐methylstyrene (AMS) was investigated by nuclear magnetic resonance (NMR). The styrene‐co‐α‐methylstyrene (SAMS) was analyzed by solution and solid‐state NMR techniques. Three copolymers of SAMS with different compositions presented a particular behavior. The solution results showed the copolymer microstructure and the AMS content. The carbon‐13 spectra of SAMS C indicated that the AMS CH₃ signal was detected at three distinct chemical shifts, because of the different comonomer‐sequences distribution. The proton spin–lattice relaxation time in the rotating frame (Tρ) parameter was chosen because it permits the evaluation of changes in the molecular mobility. The values of Tρ found for the copolymers confirmed the random distribution in the samples. The copolymer with a low quantity of AMS (1.7%), when analyzed by this relaxation parameter, showed lower values that were interpreted as an antiplasticization effect. The SAMS copolymer with a higher AMS quantity showed a plasticization effect. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 261–266, 2001     

13C‐NMR study of Dipteryx Alata Vogel starch

Natural starches obtained by fruit seeds have been a subject of studies because of their applications, as a consequence of their chemical properties. As it is known, the fruits depend on the geographic region. Because of this, several factors affect the seed starches nature, such as granules size, morphology, components, and composition. Thus, to better understand starch properties, it is necessary to investigate the chemical behavior of these factors. This work focused on the chemical components and molecular dynamic behavior of the Dipterxy Alata Vogel (cumbaru) starch, because this fruit is very popular and is used in abundance for people because they think that it is good for some kinds of diseases. The main chemical components and the molecular dynamics of starch from the Dipterxy Alata Vogel were studied by applying solid‐state ¹³C nuclear magnetic resonance spectroscopy (NMR). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2151–2154, 2004     

Experimental study on drying characteristics of wheat by low-field nuclear magnetic resonance

The characteristics of transverse relaxation time (T₂) of water in wheat were studied by measuring the relaxation time of low-field nuclear magnetic resonance. Analysis of the exponential distribution of T₂ revealed that wheat contains five water components. The T₂ relaxation time and distribution significantly changed during drying. The dynamic characteristics of five water components during wheat drying were determined using the signal quantity of their characteristic peaks, which showed different features. Weakly chemically bound water (T₂₂) and water ascribed to cell wall (T₂₃) were the main source of water loss. Moreover, most T₂₃ and extracellular water (T₂₄) were removed during drying. Water migration between strongly chemically bound water (T₂₁) and the other water components was bidirectional. This process was not only affected by temperature but also by wheat moisture content and proportion of the five water components. The start time of water migration advanced and growth rate of T₂₁ at the end of drying to that before drying increased at 60, 70, and 80°C. Drying at varied temperatures should be applied according to the characteristics of five water components during the drying process. In addition, high initial temperature was found to be necessary to achieve high drying rate of T₂₃, T₂₄, and free water (T₂₅). The use of drying temperature of 80°C at the early stage and then changing to 70°C reduced the heat consumption by 4.81% and increased the drying time by 9.61%.     

Carbon-13 nuclear magnetic resonance study of a divinylbenzene–p-cresol oligomer mixture

¹³C NMR has been found to be useful in elucidating the structure of a complex condensation product. Study of a divinylbenzene–p-cresol oligomer mixture has shown structural units consisting of approximately 85% 2,6-substituted p-cresol, 5–10% 2,5-substituted p-cresol, and 5–10% 2-substituted p-cresol endgroups.     

13C‐NMR study on the structure of phenol‐urea‐formaldehyde resins prepared by methylolureas and phenol

Phenol‐urea‐formaldehyde (PUF) resins were synthesized by reacting mixture of methylolureas (MMU), phenol, and formaldehyde. The structure of PUF cocondensed resins at different stages of reaction were analyzed by liquid ¹³C nuclear magnetic resonance (NMR) spectroscopy. The liquid ¹³C‐NMR analysis indicated that methylolureas had the dominant content in MMU with the reaction between urea and formaldehyde under the alkaline condition. The PUF cocondensed resins had no free formaldehyde. methylolureas were well incorporated into the cocondensed resins by reacting with phenolic units to form cocondensed methylene bridges. The second formaldehyde influenced the further reaction and the structure of the PUF resins. The resins with the prepared method of PUFB possessed relatively high degree of polymerization and low proportion of unreacted methylol groups. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Measuring stereoselectivity in lipase-catalyzed acidolysis reactions by ultra-high resolution 13C nuclear magnetic resonance

Elucidating the stereoselectivity of lipases in synthetic reactions of triacylglycerols has hitherto been carried out using traditional analytical techniques to determine the composition of the reaction products. These methods are laborious and are not always appropriate for analysis of certain triacylglycerol types. A direct method, utilizing a stereospecific deuterium-labeled triacylglycerol substrate, has been developed where the stereoisomeric composition of the reaction product is determined by ultra-high resolution ¹³C nuclear magnetic resonance (NMR) spectroscopy. Through lipase-catalyzed transesterification of deuterium-labeled trilauroylglycerol with oleic acid, chemical shifts were induced in the ¹³C NMR spectrum by the deuterium atom and olefinic double bonds, enabling unambiguous stereospecific assignment of triacylglycerol species. By this method of analysis, we found an effect of the degree of reaction conversion on the extent of stereoisomerism in the triacylglycerol product. Stereoselectivity was greatest (for sn-1) with lipase from Rhizomucor miehei. Lipases from Rhizopus niveus, Candida rugosa, Carica papaya, and the cutinase from Fusarium sp. were also found to exhibit stereoselectivity, with preference for either sn-1 or sn-3 acyl exchange.