Dipolar filtered magic-sandwich-echoes as a tool for probing molecular motions using time domain NMR

Filgueiras, Jefferson G.; Silva, Uilson B. da; Paro, Giovanni; d’Eurydice, Marcel Nogueira; Cobo, Marcio Fernando; deAzevedo, Eduardo R.

doi:10.1016/j.jmr.2017.10.008

Cited by 11 publications

(7 citation statements)

References 48 publications

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“…A different approach was proposed to bring out only signals of the mobile component with the use of a dipolar filter, based on the GS, followed by an MSE, to refocus the magnetization lost during the filter time [33]. In order to select the magnetization arising from mobile fractions, an early approach was the Goldman-Shen (GS) sequence [31].…”

Section: Spins' Manipulationmentioning

confidence: 99%

“…Lately, a different method for characterizing intermediate to fast regime motion ( >kHz) was proposed by Filgueiras et al [33] based on a dipolar filter, which suppresses the signal from rigid segments. Whenever some molecular segments become more mobile, the signal is no longer completely suppressed and can be refocused with an MSE block, creating an echo the more intense the higher the mobility.…”

Section: Polymer Physicsmentioning

confidence: 99%

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Time Domain NMR in Polymer Science: From the Laboratory to the Industry

2019

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Highly controlled polymers and nanostructures are increasingly translated from the lab to the industry. Together with the industrialization of complex systems from renewable sources, a paradigm change in the processing of plastics and rubbers is underway, requiring a new generation of analytical tools. Here, we present the recent developments in time domain NMR (TD-NMR), starting with an introduction of the methods. Several examples illustrate the new take on traditional issues like the measurement of crosslink density in vulcanized rubber or the monitoring of crystallization kinetics, as well as the unique information that can be extracted from multiphase, nanophase and composite materials. Generally, TD-NMR is capable of determining structural parameters that are in agreement with other techniques and with the final macroscopic properties of industrial interest, as well as reveal details on the local homogeneity that are difficult to obtain otherwise. Considering its moderate technical and space requirements of performing, TD-NMR is a good candidate for assisting product and process development in several applications throughout the rubber, plastics, composites and adhesives industry.

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Section: Spins' Manipulationmentioning

confidence: 99%

Section: Polymer Physicsmentioning

confidence: 99%

Time Domain NMR in Polymer Science: From the Laboratory to the Industry

2019

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“…Molecules 2022, 27, 566 2 of 14 Among the NMR methods, 1 H TD-NMR at a low magnetic field is particularly useful for studying molecular processes where chemical specificity is not necessary. Indeed, because of its high sensitivity to molecular mobility, TD-NMR can detect dynamical chances associated to thermal transitions [5][6][7][8]. In addition, the technique allows to determine other important information such as the ratio between rigid and mobile segments, sizes of molecular clusters in emulsions [9], determination of the degree of crystallinity and crystallite sizes in semicrystalline systems [10], gelation rates in polymer gels [11] and crosslinking and entanglement in elastomers [12][13][14], among others [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Real-Time Monitoring Polymerization Reactions Using Dipolar Echoes in 1H Time Domain NMR at a Low Magnetic Field

et al. 2022

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1H time domain nuclear magnetic resonance (1H TD-NMR) at a low magnetic field becomes a powerful technique for the structure and dynamics characterization of soft organic materials. This relies mostly on the method sensitivity to the 1H-1H magnetic dipolar couplings, which depend on the molecular orientation with respect to the applied magnetic field. On the other hand, the good sensitivity of the 1H detection makes it possible to monitor real time processes that modify the dipolar coupling as a result of changes in the molecular mobility. In this regard, the so-called dipolar echoes technique can increase the sensitivity and accuracy of the real-time monitoring. In this article we evaluate the performance of commonly used 1H TD-NMR dipolar echo methods for probing polymerization reactions. As a proof of principle, we monitor the cure of a commercial epoxy resin, using techniques such as mixed-Magic Sandwich Echo (MSE), Rhim Kessemeier—Radiofrequency Optimized Solid Echo (RK-ROSE) and Dipolar Filtered Magic Sandwich Echo (DF-MSE). Applying a reaction kinetic model that supposes simultaneous autocatalytic and noncatalytic reaction pathways, we show the analysis to obtain the rate and activation energy for the epoxy curing reaction using the NMR data. The results obtained using the different NMR methods are in good agreement among them and also results reported in the literature for similar samples. This demonstrates that any of these dipolar echo pulse sequences can be efficiently used for monitoring and characterizing this type of reaction. Nonetheless, the DF-MSE method showed intrinsic advantages, such as easier data handling and processing, and seems to be the method of choice for monitoring this type of reaction. In general, the procedure is suitable for characterizing reactions involving the formation of solid products from liquid reagents, with some adaptations concerning the reaction model.

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“…Esta característica especial permite seu uso como um bloco de sequência de pulsos mais complexas. [32] A parte "sandwich" da sequência é composta de dois blocos de quatro pulsos de 90°, onde a fase do segundo bloco é invertida em 180° da fase do primeiro. Por fim, após um tempo de espera surge o eco que refocaliza os sinais de materiais sólidos, ou seja, com interações dipolares 1 H-1 H. Na…”

Section: Sequências De Pulsos Utilizadas Em Rmn-dt No Estado Sólidounclassified

“…Os filtros dipolar são amplamente utilizadas como blocos de construção em sequências de pulso para estudar nano-heterogeneidade em polímeros através de experiências de difusão de spins, [82] regime intermediário de dinâmica molecular [83] e processos de cristalização. [84][85] Dada a grande aplicabilidade dos filtros dipolares em experimentos de RMN, propomos aqui…”

Section: Aplicação Da Sequência De Pulso Rk-rose Como Filtro De Fase Móvelunclassified

Desenvolvimento da sequência de pulso RK-ROSE e aplicações em RMN-DT para analise de componentes sólidos

Garcia¹

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Time domain nuclear magnetic resonance (TD-NMR) typically use lowcost benchtop equipment. TD-NMR is used for both homogeneous and heterogeneous material analyses, in quality control of food, petroleum and derivatives, cosmetics and polymers. Even in the case of heterogeneous materials containing solid and liquid substances, TD-NMR analyzes are mainly based on the liquid part, which has a slow decay, even seconds, due to the high molecular mobility. The analysis of solid components in foods, polymers and other organic materials are studied in less extensión, because the signal decays in some microseconds and are difficult to detect. The purpose of this doctoral thesis is to evaluate the performance of a new pulse sequence designed to refocus the signals of the rigid components of a sample. The main advantage of these sequences is that for its application it is not need extra accessories and therefore can be applied to bench-top TD-NMR equipment and cheap. A new pulse sequence called Rhim-Kessemeier-Radiofrequency Optimized Solid-Echo (RK-ROSE) has been proposed that has higher efficiency than the most commonly used sequences for solid state sample characterization and reaction kinetics monitoring, for example, the Solid-Echo (ES) sequence and "mixed -Magic Sandwich Echo" (mixed-MSE). The RK-ROSE sequence has been evaluated for some applications which include: a) determination of solid components in different samples, for example for polystyrene (PS) and the sequence provided approximately 98% efficiency; b) to solve the reaction kinetics parameters, such as velocity constant (Kc) at different temperatures and to determine the activation energy ( ) of the Araldite epoxy resin polymerization; c) as a method for determining spin-lattice or spin-longitdinal (T 1 ) and spin-spin (T 2 ) relaxation time in solid materials, resulting in 2D experiments to obtain T 1 and T 2 ; d) as a mobile phase filter in experiments to study the molecular dynamics of polymers at different temperatures; and e) as an alternative method to determine solid fat content (SFC) in different samples of butter and cocoa butter, this new method had satisfactory results with the advantage of not using calibration standards.

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Dipolar filtered magic-sandwich-echoes as a tool for probing molecular motions using time domain NMR

Cited by 11 publications

References 48 publications

Time Domain NMR in Polymer Science: From the Laboratory to the Industry

Time Domain NMR in Polymer Science: From the Laboratory to the Industry

Real-Time Monitoring Polymerization Reactions Using Dipolar Echoes in 1H Time Domain NMR at a Low Magnetic Field

Desenvolvimento da sequência de pulso RK-ROSE e aplicações em RMN-DT para analise de componentes sólidos

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