1H time domain NMR real time monitoring of polyacrylamide hydrogels synthesis

Rodrigues, Elton Jorge da Rocha; Sebastião, Pedro J.; Tavares, Maria Inês Bruno

doi:10.1016/j.polymertesting.2017.04.028

Cited by 9 publications

(15 citation statements)

References 30 publications

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“…. High monomer conversion values were achieved in the first 30 min of polymerization, a result in good agreement with Giz et al ., Rodrigues et al . and Orakdogen and Okay .…”

Section: Resultssupporting

confidence: 90%

“…The conversion measurements for the P1 − P9 series were performed on a UV–visible equipment (Biospectro SP‐220) at 25 °C, calibrated with a blank sample consisting of distilled water, initiator and TEMED in the amounts described in Table and adjusted to measure the absorbance at 275 nm, corresponding to the absorption of the unsaturated carbon–carbon bond present in Aam . The decrease in absorbance was measured every 5 min from the addition of TEMED and subsequently transformed into conversion values via

ξ = 1 - m_{t} false/ m_{0}

where ξ is the conversion of monomer to polymer and ranges from 0 to 1, m t is the absorbance value measured at time t and m 0 is the absorbance value measured at the beginning of the reaction.…”

Section: Methodsmentioning

confidence: 99%

“…During the TD‐NMR real‐time monitoring, the polymerization reactions were conducted at 27 °C (probe air flow temperature controller, ±0.01 °C resolution) in NMR glass tubes (18 mm outer diameter) containing the reaction mixture and sealed with silicone septa. The tubes were inserted into the spectrometer (Maran Ultra 0.54 T) probe, where the monitoring was performed by the use of Carr−Purcell CWFP (CP‐CWFP)

normalRD bold- ((), \frac{π}{2}) bold- τ bold- {[(\frac{π}{2}) - echo - (\frac{π}{2})]}_{n}

…”

Section: Methodsmentioning

confidence: 99%

“…The curves appear different from each other, depending on reaction time and formulation. This is because the shape of the curves is determined by the reaction system's T 1 and T 2 values, as given by Eqns −(5), which are expected to vary according to the molecular dynamics changes experienced during the polymerization reactions:

M_{s} = \frac{M_{0} T_{2}}{T_{1} + T_{2}}

T^{*} = \frac{2 T_{1} T_{2}}{T_{1} + T_{2}}

T_{1} = \frac{\frac{T^{*}}{2}}{\frac{M_{s}}{M_{0}}}

T_{2} = \frac{\frac{T^{*}}{2}}{1 - ((), \frac{M_{s}}{M_{0}})}

…”

Section: Methodsmentioning

confidence: 99%

“…In a previous paper, the potential of proton TD‐NMR for real‐time monitoring of the polymerization crosslinking of acrylamide‐based hydrogels was demonstrated by our group. However, no further discussion of the observed changes in the relaxation constants as a function of reaction time and medium was offered at the time.…”

Section: Introductionmentioning

confidence: 96%

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Real‐time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution

Rodrigues¹,

Neto²,

Sebastião

et al. 2018

Polymer International

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The potential of time‐domain nuclear magnetic resonance (TD‐NMR) for the real‐time monitoring of solution radical polymerizations is demonstrated. A model system composed of a redox‐pair initiator system, acrylamide as monomer and water as solvent was investigated. A second‐generation continuous wave free precession technique was employed to measure the longitudinal relaxation time constant (T1) of the samples throughout the polymerization reactions. This parameter was shown to be sensitive to the reactant feed free‐radical enhancement of the water molecule relaxation time, making it a good probe to monitor monomer conversion in real time in an automated, non‐destructive fashion. It was found that the T1 value was better than the transverse relaxation time constant (T2) for describing the evolution of the polymerization reactions, due to its greater sensitivity to paramagnetic effects. The TD‐NMR signal variation observed was linked to the formation, propagation and termination steps of the radical polymerization kinetics scheme. These first results may contribute to the application of real‐time monitoring of radical polymerization reactions employing low‐cost and robust TD‐NMR spectrometers. © 2018 Society of Chemical Industry

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“…. High monomer conversion values were achieved in the first 30 min of polymerization, a result in good agreement with Giz et al ., Rodrigues et al . and Orakdogen and Okay .…”

Section: Resultssupporting

confidence: 90%

ξ = 1 - m_{t} false/ m_{0}

Section: Methodsmentioning

confidence: 99%

normalRD bold- ((), \frac{π}{2}) bold- τ bold- {[(\frac{π}{2}) - echo - (\frac{π}{2})]}_{n}

…”

Section: Methodsmentioning

confidence: 99%

M_{s} = \frac{M_{0} T_{2}}{T_{1} + T_{2}}

T^{*} = \frac{2 T_{1} T_{2}}{T_{1} + T_{2}}

T_{1} = \frac{\frac{T^{*}}{2}}{\frac{M_{s}}{M_{0}}}

T_{2} = \frac{\frac{T^{*}}{2}}{1 - ((), \frac{M_{s}}{M_{0}})}

…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

See 3 more Smart Citations

Real‐time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution

Rodrigues¹,

Neto²,

Sebastião

et al. 2018

Polymer International

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Single‐shot measurement of solids and liquids T₁ values by a small‐angle flip‐flop pulse sequence

Neto

Rodrigues

Tavares

2019

Magnetic Reson in Chemistry

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We propose the small‐angle flip‐flop (SAFF) pulse sequence as an alternative procedure for the rapid measurement of the 1H spin–lattice relaxation time in the laboratory frame (T1) of solid and liquid substances, in a time‐domain NMR experiment. Based on the original flip‐flop pulse sequence, this technique allows the fast estimation of T1 values of samples that require minutes to hours of acquisition time if traditional pulse sequences are employed. We have applied SAFF to different substances, with T1 ranging from microseconds up to seconds, including natural clays, polymers, and organic and inorganic solvents. We also demonstrate the potential of the pulse sequence in the real‐time monitoring of dynamic processes, such as the conformational changes of polymeric materials during heating. The results we obtained with SAFF are comparable with those acquired with the inversion‐recovery pulse sequence, with the addition of several benefits. This pulse sequence obeys steady‐state and magnetization‐conserving principles, making it possible to dismiss the need for relaxation delay times of the order of 5T1. SAFF has shown high sensitivity in the resolution of individual components of T1 in multiexponential systems and can be easily integrated to well‐established pulse sequences, such as Magic Sandwich Echo and Carr–Purcell–Meiboom–Gill, for the single‐shot determination of T1 and T2 or T2*.

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An investigation of the fluid-holding cavities in a lignocellulose-based bamboo matrix via a combined X-ray microtomography and proton time-domain NMR approach

et al. 2023

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Bamboo (Dendrocalamus giganteus) is a functionally graded material with well-organized hierarchical structures. Its micrometer-sized vascular bundles and parenchymatic living cells allow an efficient upward flow of water and nutrients, endowing the organism with remarkably fast growth. As demonstrated recently, the hollow microstructure channels can be explored as a natural template for microfluidics applications in chemical synthesis, analytical detection, solar steam generation, and electrochemical devices. Thus, the knowledge of the kinetics of the imbibition and spatial distribution of fluid through the microcavities of the bamboo vegetal tissue became of interest. Here, we employed a combination of X-ray microtomography (µCT) and proton time-domain NMR (TD-NMR) to identify, measure, and investigate empty volumes embedded in the bamboo’s tissue as experienced by different organic and inorganic fluids, namely dimethyl sulfoxide (DMSO) and distilled water (H2O). Results have shown that the extensive communication between the voids (parenchymal cells and vascular channels) does not prevent the individuation of fluid reservoirs with different behaviors, as evidenced by the H2O desorption profile. Bamboo parenchyma was the tissue that retained more residual H2O after desorption. The difference in wettability of bamboo tissues by DMSO and H2O was detected. Graphical abstract

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1H time domain NMR real time monitoring of polyacrylamide hydrogels synthesis

Cited by 9 publications

References 30 publications

Real‐time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution

Real‐time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution

Single‐shot measurement of solids and liquids T₁ values by a small‐angle flip‐flop pulse sequence

An investigation of the fluid-holding cavities in a lignocellulose-based bamboo matrix via a combined X-ray microtomography and proton time-domain NMR approach

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1H time domain NMR real time monitoring of polyacrylamide hydrogels synthesis

Cited by 9 publications

References 30 publications

Real‐time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution

Real‐time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution

Single‐shot measurement of solids and liquids T1 values by a small‐angle flip‐flop pulse sequence

An investigation of the fluid-holding cavities in a lignocellulose-based bamboo matrix via a combined X-ray microtomography and proton time-domain NMR approach

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Product

Resources

About

Single‐shot measurement of solids and liquids T₁ values by a small‐angle flip‐flop pulse sequence