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FT-IR spectra expansion of (a) short-chain aliphatic aldehyde C-H region and (b) aldehyde carbonyls and of C-C or C-O bonds.
Source publication
Poly(vinyl alcohol) (PVA)-based chemically cross-linked xerogels, both neat and loaded with nanoparticulate hydrophilic silica (SiO2), were obtained and characterized mainly through time domain NMR experiments (TD-NMR). Fourier-transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD) analyses were employed as secondary methods. TD-NMR, th...
Contexts in source publication
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... the spectra of PVA and of PVA/SiO 2 there are no apparent differences, which implies weak intermolecular interactions between the polymer matrix and inorganic nanoparticles (Figure 2a). For better visualization, we selected and expanded regions of the FT-IR spectra from PVA and P10 samples, as shown in Figure 3a, b. All the xerogels display absorption bands at 2850-2750 cm -1 (Figure 3a) and 1720-1750 cm -1 (Figure 3b), corresponding to absorption modes of short-chain aliphatic aldehyde C-H and aldehyde carbonyls, which indicates some incomplete cross-linking. ...
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... better visualization, we selected and expanded regions of the FT-IR spectra from PVA and P10 samples, as shown in Figure 3a, b. All the xerogels display absorption bands at 2850-2750 cm -1 (Figure 3a) and 1720-1750 cm -1 (Figure 3b), corresponding to absorption modes of short-chain aliphatic aldehyde C-H and aldehyde carbonyls, which indicates some incomplete cross-linking. Although faint, the increase in the intensity of the absorption bands arising from cross-linking and the decrease in the intensity of the 1141 cm -1 band (Figure 3b), relative to spatial order in the PVA matrix, can be distinguished in the spectra. ...
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... better visualization, we selected and expanded regions of the FT-IR spectra from PVA and P10 samples, as shown in Figure 3a, b. All the xerogels display absorption bands at 2850-2750 cm -1 (Figure 3a) and 1720-1750 cm -1 (Figure 3b), corresponding to absorption modes of short-chain aliphatic aldehyde C-H and aldehyde carbonyls, which indicates some incomplete cross-linking. Although faint, the increase in the intensity of the absorption bands arising from cross-linking and the decrease in the intensity of the 1141 cm -1 band (Figure 3b), relative to spatial order in the PVA matrix, can be distinguished in the spectra. ...
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... the xerogels display absorption bands at 2850-2750 cm -1 (Figure 3a) and 1720-1750 cm -1 (Figure 3b), corresponding to absorption modes of short-chain aliphatic aldehyde C-H and aldehyde carbonyls, which indicates some incomplete cross-linking. Although faint, the increase in the intensity of the absorption bands arising from cross-linking and the decrease in the intensity of the 1141 cm -1 band (Figure 3b), relative to spatial order in the PVA matrix, can be distinguished in the spectra. Quantification of the influence of these covalent bonds on the polymeric matrix proved to be somewhat difficult and prone to experimental errors. ...
Citations
... Time-domain nuclear magnetic resonance (TD-NMR) is an efficient, fast, and non-destructive way to probe fluid behavior in confined environments (Steele et al. 2016;Singer et al. 2018). It is widely used in the study of oil reservoir rock matrices (Muhammad et al. 2014;Plastino et al. 2017;Rudszuck et al. 2019), water trapped in hydrogels (Rodrigues et al. 2016(Rodrigues et al. , 2017Ratzsch et al. 2017) and to study the molecular dynamics of liquids during the hardening of cementitious materials (Valckenborg et al. 2001;Jansen et al. 2018). ...
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.
... The longitudinal (T 1 ) relaxation time was fitted by inversion-recovery (IR). Inversion-recovery (T 1 )was accomplished in the time intervals, considering forty points spaced logarithmically at a range of 0.1 to 5000 ms, with a recycle interval of 3 s and 8 accumulations[17]. ...
... This increase in the molecular mobility also indicates weak interactions between the polymer chains and cellulose, since the separation between chains allowed them to move with more freedom. 32 The material containing 0.50% cellulose showed higher T 1 H value, showing that this cellulose content caused greater rigidity. This was probably due to the formation of strong intermolecular interactions that restricted the molecular mobility of hydrogen groups. ...
Hybrid films of poly(3-hydroxybutyrate) (PHB) and modified cellulose by solution casting method were prepared, aiming to study the influence of modified cellulose (0.25%, 0.5% and 0.75% w/w) on the structural organization and thermal properties of PHB matrix. The modified cellulose showed good dispersion in polymer matrix, due to the high compatibility between phases explained by similarity of polymer and filler structures. The composites were studied by wide-angle X-ray diffractometry, differential scanning calorimetry, thermogravimetric analysis, and time-domain nuclear magnetic resonance (NMR) spectroscopy. The conjugation of results coming from those techniques allowed to determine the cellulose concentration that had the highest influence on crystalline planes and degree of crystallinity of PHB, that is, the influence in the composite structure. The molecular dynamics obtained by NMR showed a reciprocal influence between polymer matrix and cellulose particles, enhancing the interactions present in the agglomerated particles.
... The data were processed in commercial software packages, namely WinFit version 2.4.0.0 and Origin version 8.5. Table III shows the analytical parameters used to measure samples relaxation times [3,8]. ...
... Where M (τ) is the magnetization as a function of time between 180 o and 90 o pulses; A 0 is the baseline adjustment constant, which corrects the noise associated with the relaxation signal; A 1 is a factor proportional to the number of relaxing proton nuclei in each interval and with relaxation interval between each pulse that necessarily needs to be 5 times higher than the highest value of T 1 H; τ is the time interval between 180° and 90° pulses; and T 1 H is the spinlattice relaxation time constant [3,8]. The acquired signal decay (M(t)) for CMC hydrogel and CMC-papain hydrogel samples was better fitted using 4 and 3 simple exponentials decay that returned a minor chi-square value, respectively. ...
NMR relaxometry proved to be a powerful tool that provides useful information on the molecular dynamics of different pharmaceutical materials. The proton NMR relaxometry was measured using low-field NMR equipment. The aim of this work was to evaluate the interaction of different drugs in pharmaceutical systems, such as: propranolol (POP) and atorvastatin (ATV) in tablets with Tapioca Starch (TS); POP in Rosa Mosqueta oil nanoemulsion (NE); and papain in carboxymethylcelulose (CMC) hydrogel, using the proton spin-lattice relaxation time parameter. The spin-lattice relaxation measurements (T 1 H) were done through the inversion-recovery pulse sequence and the spin-spin relaxation measurements (T 2 H) were done by two pulse sequences, one was Magic-Sandwich Eco (MSE) and the other was Carr-Purcell-Meiboom-Gill (CPMG). From the analyses of T 1 H data it was concluded that there was an interaction between the drugs and TS in the tablets, which is explained by the increase of T 1 H values. The evaluation of T 2 H relaxation time of NE confirmed a correlation between NE phases and it was observed that POP was effectively distributed in water phase. From the structure of CMC hydrogel it was observed that papain interacted with free water molecules of the hydrogel. This study confirmed that NMR relaxometry can be used to characterize the drug delivery systems.
... Removing the water out of a chemically crosslinked gel, a xerogel is obtained. In reference [54], PVA crosslinked with glutaraldehyde (GA) was characterized taking 1 H T 1 as structure descriptor. It turned out to be very sensitive both to crosslinking degree and to loading with silica, both of them inducing a reduction in 1 H T 1 due to the decreased number of hydroxyl moieties available for hydrogen bonding. ...
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.
... Fig. 3 shows the FTIR spectra of the materials obtained after the esterification reaction. The success of the reaction is verified by the appearance of a new peak in the carbonyl area located at 1737 cm −1 (C=O bond) and a wide band centered at 1250 cm −1 that is from the C-O stretching of O-(C=O)-CH 3 group [4,[17][18][19][20][21]. The peaks located at 3374, 2902, 1430, 1373 and 897 cm −1 are associated with cellulose type I [4]. ...
... The peak located at 897 cm −1 signals the β-glucopyranose bond between the celluloses. The peaks observed at 1380 and 1320 cm −1 are attributed to the axial vibration of the C-H and C-O bond of polysaccharide ring, respectively [1,13,20]. Finally, the absence of peak in the regions between 1840 and 1760 cm −1 shows the effectiveness of the final stage of the process modification due to the removal of non-reactive acetic acid, which agrees with the literature [4,20]. ...
... The peaks observed at 1380 and 1320 cm −1 are attributed to the axial vibration of the C-H and C-O bond of polysaccharide ring, respectively [1,13,20]. Finally, the absence of peak in the regions between 1840 and 1760 cm −1 shows the effectiveness of the final stage of the process modification due to the removal of non-reactive acetic acid, which agrees with the literature [4,20]. ...
More ecofriendly packaging can be obtained with the use of cellulose as a reinforcement and barrier. For this work, cellulose particles were incorporated in EVA matrix to obtain transparent EVA composite films with cellulose particles at different concentrations focusing on the improvement of the barrier properties. The films were obtained by solution casting. Commercial microcrystalline cellulose (MCC) was modified with glacial acetic acid, reducing the particle size. These modifications were monitored by FTIR, XRD, NMR and SEM. The composites formed by EVA/MCC were characterized by XRD, thermogravimetric analysis and mechanical properties to understand the influence of these particles on the displacement of the crystalline planes of the polymer matrix. The degree of crystallinity was also altered as larger concentrations of cellulose were added to EVA. TGA results showed no significant changes in the thermal degradation temperature of the material and, from DSC, it was seen that cellulose did not behave as a nucleating agent in EVA. The storage modulus obtained from the DMA analysis was inversely proportional to the cellulose content, indicating that there was an increase in the rigidity of the material caused by the dispersion of cellulose, which acts as a material reinforcement. These data were corroborated by the increase in the proton spin-lattice relaxation time values determined by NMR relaxometry technique, which provides information on sample molecular behavior, confirming the molecular interaction between material components.
... Among the spectroscopic techniques, proton nuclear magnetic resonance ( 1 H NMR) relaxometry is becoming more and more an established experimental technique used for the characterization of different materials, in particular polymer based systems [6][7][8][9][10]. ...
Synthesis reactions of polyacrylamide based hydrogels were automatically monitored in situ by time-domain nuclear magnetic resonance, through a steady-state pulse sequence. Four hydrogel formulations with different amounts of monomer and crosslinking agent were tested and the proposed method demonstrated sensitivity to each formulation without the need for a priori calibration of the spectrometer, even when the hydrogels exhibited substantially different structural characteristics. The results obtained by the proposed method were compared for validation with those generated by traditional reaction monitoring methods, such as UV-Vis spectroscopy, and exhibited similar results, suggesting that time-domain nuclear magnetic constitutes an interesting alternative for the monitoring of solution crosslinking reactions.
... This kind of polymer combination is already known in pharmaceutical field, however, this study focused on structural and molecular mobility evaluation with new perspectives by using TD-NMR. Since it provides information about material structure and properties, as well as allowing detailed study of crystalline and amorphous domains [20], 1 H relaxometry has been widely employed to evaluate polymer molecular dynamics [21,22], including for drug delivery applications [23]. ...
The relationship between molecular structure and water dynamics is a fundamental yet often neglected subject in the field of hydrogels for drug delivery, bioprinting, as well as biomaterial science and tissue engineering & regenerative medicine (TE&RM). Water is a fundamental constituent of hydrogel systems and engages via hydrogen bonding with the macromolecular network. The methods and techniques to measure and reveal the phenomena and dynamics of water within hydrogels are still limited. In this work, differential scanning calorimetry (DSC) was used as a quantitative method to analyze freezable (including free and freezable bound) and non-freezable bound water within gelatin methacrylate (GelMA) hydrogels. Nuclear magnetic resonance (NMR) is a complementary method for the study of water behavior and can be used to measure the spin-relaxation of water hydrogen nuclei, which is related to water dynamics. In this research, nuclear magnetic resonance relaxometry was employed to investigate the molecular state of water in GelMA hydrogels using spin-lattice (T1) and spin-spin (T2) spin-relaxation time constants. The data displays a trend of increasing bound water content with increasing GelMA concentration. In addition, T2 values were further applied to calculate microviscosity and translational diffusion coefficients. Water relaxation under various chemical environments, including different media, temperatures, gelatin sources, as well as crosslinking effects, were also examined. These comprehensive physical data sets offer fundamental insight into biomolecule transport within the GelMA hydrogel system, which ultimately are important for drug delivery, bioprinting, as well as biomaterial science and TE&RM communities.
Starch/polyvinyl alcohol (PVA) degradable straws with different PVA contents were prepared by the twin-screw extrusion method. The results showed that the starch/PVA straws with 40 % PVA (PS4) had the highest dispersion uniformity of starch and PVA to achieve the best compatibility, and the compatibility size was below the micron level. Molecular interactions between starch and 40 % polyvinyl alcohol reached the highest due to the highest strength of hydrogen bonds, hence resulting in the highest texture densities. Consequently, the largest compatibility and molecular interactions significantly improved the mechanical properties and water resistance of PS4. Compared to the starch/PVA straw with 0 % PVA (PS0), swelling volume of PS4 decreased by 45.5 % (4 °C) and 65.2 % (70 °C), respectively. After soaking, the diameter strength increased by 540.1 % (4 °C, 1 h) and 638.7 % (70 °C, 15 min), respectively. Water absorption decreased by 45.3 % (4 °C, 30 min) and 27.6 % (70 °C, 30 min).
