Quantitative Analysis of Hydrogen Bonding in Poly(4-Vinylphenol) Blends Using near Infrared Spectroscopy

2003 ◽  
Vol 11 (3) ◽  
pp. 183-191 ◽  
Author(s):  
Haijun Cai ◽  
Josée Brisson
Keyword(s):  
Hydrogen Bonding ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Weight Fraction ◽  
Hydroxyl Groups ◽  
Absorption Coefficients ◽  
Oh Groups ◽  
Refinement Method ◽  
Poly Ethylene ◽  
Vinyl Phenol

Quantitative evaluation of hydrogen bonding of poly(4-vinyl phenol)/poly(ethylene oxide) PVPh/PEO blends was conducted using Fourier transform near infrared (FT-NIR) spectroscopy. Absorption coefficients of the free ( aF), intra- (PVPh–PVPh) ( aA) and inter-associated (PVPh–PEO) hydroxyl groups ( aI) were estimated. Two sets of approximations were tested, including adopting a least-squares refinement method to calculate absorption coefficients from all NIR spectra or using a literature value for aF. Each set of absorption coefficients thus estimated were used to determine hydroxyl concentration for the free and hydrogen-bonded hydroxyl overtone bands in the blends. A comparison is made among the resultant concentrations of the free, intra- and inter-associated hydroxyl groups. The concentration of free hydroxyl groups markedly decreases with PEO percentage, and that of intra-associated hydroxyl remains almost constant. Concentration for the inter-associated hydroxyl groups in the blends increases very slowly above 0.2 PEO weight fraction. When concentration of OH groups is reported per PVPh chain, FT-NIR measurements show a broad maximum in the number of interchain hydrogen bonds. This result can be used to explain partially previous orientation behaviour observed for PVPh/PEO blends.

Proton spin–spin coupling constants and intramolecular hydrogen bonding in bromine derivatives of 1,3-dihydroxybenzene

1976 ◽  
Vol 54 (14) ◽  
pp. 2228-2230 ◽  
Author(s):  
Ted Schaefer ◽  
J. Brian Rowbotham
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of

The conformational preferences in CCl4 solution at 32 °C of the hydroxyl groups in bromine derivatives of 1,3-dihydroxybenzene are deduced from the long-range spin–spin coupling constants between hydroxyl protons and ring protons over five bonds. Two hydroxyl groups hydrogen bond to the same bromine substituent in 2-bromo-1,3-dihydroxybenzene but prefer to hydrogen bond to different bromine substituents when available, as in 2,4-dibromo-1,3-dihydroxybenzene. When the OH groups can each choose between two ortho bromine atoms, as in 2,4,6-tribromoresorcinol, they apparently do so in a very nearly statistical manner except that they avoid hydrogen bonding to the common bromine atom.

Study of the Infrared Spectral Features of an Epoxy Curing Mechanism

2008 ◽  
Vol 62 (10) ◽  
pp. 1129-1136 ◽  
Author(s):  
Liang Li ◽  
Qili Wu ◽  
Shanjun Li ◽  
Peiyi Wu
Keyword(s):  
Correlation Analysis ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Diglycidyl Ether ◽  
Hydroxyl Groups ◽  
Spectral Correlation ◽  
Derivative Analysis ◽  
Curing Mechanism ◽  
Infrared Spectral ◽  
Epoxy Groups

In this work, the isothermal curing process of diglycidyl ether of bisphenol A(DGEBA) cured with 4,4′-diaminodiphenylmethane (DDM) was monitored in situ by mid-infrared (MIR) and near-infrared (NIR) spectroscopy. With the help of generalized two-dimensional (2D) correlation analysis, the results obtained showed that, during curing, the change of amine and epoxy groups was simultaneous, taking place prior to the change of hydroxyl groups, followed by the change of CH2/CH groups, resulting from the ring-opening reaction of epoxy groups. In addition, 2D MIR×NIR hetero-spectral correlation analysis and second-derivative analysis were also employed, by means of which direct evidence of the curing mechanism could be obtained and obscure NIR band assignments in the overlapped CH combination region could be made.

scholarly journals Water Adsorption Properties of Free and Dehydrated β-Cyclodextrin Studied by near Infrared Spectroscopy and Gravimetry

2016 ◽  
Vol 689 ◽  
pp. 143-147 ◽  
Author(s):  
Alfred A. Christy
Keyword(s):  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Water Adsorption ◽  
Near Infrared ◽  
Adsorption Properties ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Near Infrared Spectra ◽  
Adsorption Of Water

β-cyclodextrin, like other carbohydrates has a tendency to adsorb water molecules and the properties are attributed to the hydroxyl groups in the molecules. β-cyclodextrin, the cyclic oligomer of glucose has a hydrophobic interior and hydrophilic exterior. The cyclic structure favours the formation of hydrogen bonds between the OH groups on the adjacent glucose units and affects the formation of hydrogen bonds with water molecules. The hydoxyl groups engaged in hydrogen bondings can be eliminated at high temperatures and the adsorption properties of the dehydrated β-cyclodextrin will depend on the new functional groups formed. The aim of the report is to discuss the issue of the water adsorption properties of free and dehydrated β-cyclodextrin. Dry β-cyclodextrin and dehydrated β-cyclodextrin at temperatures 250, 300 and 350 °C were allowed to adsorb water from a humidity controlled air environmennt and the evolving near infrared spectra were measured using a near infrared spectrometer equipped with a transflectance accessory. The near infrared spectra in the region 10,000-4000 cm-1 and their second and fourth derivative profiles were used in studying the variation in the adsorption characteristics of dehydrated β-cyclodextrin. The results of the analyses show that the adsorption of water by β-cyclodextrin decreses at 300 °C compared to 200 and 250 °C. Dehydration forms more of the ethereal type-O-bonds in the molecule and explains the decrease in the water molecular adsorption at higher dehydration temperatures.

scholarly journals Some Applications of Vibrational Spectroscopy for the Analysis of Polymers and Polymer Composites

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1159 ◽  
Author(s):  
Liliane Bokobza
Keyword(s):  
Polymer Composites ◽  
Vibrational Spectroscopy ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Polymeric Materials ◽  
Molecular Structures ◽  
Hydroxyl Groups ◽  
Inorganic Particles ◽  
Reinforcing Fillers

Vibrational spectroscopies, including infrared and Raman techniques, are important tools for the characterization of chemical composition, molecular structures, and chain orientation under mechanical deformation of polymeric materials. The development of fiber-optic-based spectrometers has broadened the use of vibrational spectroscopy for process monitoring in various fields including polymerization, curing, and manufacturing processes. Combined with chemometrics, near-infrared (NIR) spectroscopy is now recognized as one of the most important techniques for polymer analyses. Infrared and Raman studies also offer invaluable means for the analysis of inorganic particles used as reinforcing fillers for polymers. The characterization of surface species and the nature of interfacial bonding between the organic and inorganic phases are important issues for the understanding of composite properties. Infrared spectroscopy is particularly convenient for the detection and analysis of hydroxyl groups on filler surfaces, and Raman spectroscopy is particularly well suited for the study of carbon-based materials. In both techniques, polymer-filler interactions can be evidenced through frequency shifts or width changes of bands associated with vibrational modes of functional groups of either macromolecular chains or filler particles. Selected examples of application of infrared and Raman spectroscopies illustrate their potential for monitoring polymer processes, measuring polymer orientation, and characterizing polymer composites.

Perturbation effects due to hydrogen bonding in physical adsorption studied by length-change and infra-red techniques

1958 ◽  
Vol 246 (1244) ◽  
pp. 32-51 ◽  
Keyword(s):  
Hydrogen Bonding ◽  
Physical Adsorption ◽  
Porous Silica ◽  
Length Change ◽  
Hydroxyl Groups ◽  
Adsorbed Molecules ◽  
Oh Groups ◽  
Adsorption Sites ◽  
Infra Red ◽  
Length Changes

Effects due to hydrogen bonding between physically adsorbed molecules and the hydroxyl groups present on the surface of porous silica glass have been studied. Three methods have been used. As well as the classical isotherms, length changes of the adsorbent have been measured using an interferometer, and infra-red absorption spectra have been obtained both of the surface OH groups and the adsorbed molecules. Contractions of the rigid adsorbent, found under certain conditions at low coverages, are shown to be directly related to the strengths and number of the hydrogen bonds formed between the OH groups and the adsorbed molecules. More than half the surface OH groups were replaced by OCH 3 groups by methylation. Experiments performed on the glass after this treatment showed that the contractions had almost completely disappeared. It has been shown that two types of adsorption sites exist, one being the OH groups and the other the silicon or oxygen atoms. With acetone and ammonia, it has been shown spectroscopically that the energy of adsorption is lower on the OH sites than on the others. Consequently, as the temperature is raised the distribution of the adsorbed molecules between the two sites changes. Thus the marked decrease in the contractions with increase of temperature reported previously (Folman & Yates 1958) is due to the weakening of the hydrogen bonding with increase in temperature and also to a decrease in the relative numbers of the adsorbed molecules which are hydrogen-bonded. On the basis of all the results, a model of the surface conditions is proposed, which may explain the occurrence of the contractions found when hydrogen bonding is operative.

Structural Investigations and Monitoring of Polymerisation by NIR Spectroscopy

1998 ◽  
Vol 6 (1) ◽  
pp. 299-306 ◽  
Author(s):  
Gilbert Lachenal
Keyword(s):  
Hydrogen Bonding ◽  
Water Content ◽  
Physical State ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Relevant Information ◽  
Degree Of Cure ◽  
Structural Investigations ◽  
Mechanism Of Reaction ◽  
Cure Mechanism

Near infrared (NIR) spectra can give relevant information on the chemical and physical state of polymers and polymeric composites. Degree of cure, mechanism of reaction, crystallinity, orientation, water content and hydrogen bonding can be studied using NIR spectra without any sophisticated mathematical treatments. Some NIR applications are reviewed.

EXAFS study on the neptunium(V) complexation by various humic acids under neutral pH conditions

2005 ◽  
Vol 93 (1) ◽  
Author(s):  
S. Sachs ◽  
K. Schmeide ◽  
T. Reich ◽  
V. Brendler ◽  
K. H. Heise ◽  
...  
Keyword(s):  
Humic Acid ◽  
Near Infrared ◽  
Structural Parameters ◽  
Cation Exchange Resin ◽  
Nir Spectroscopy ◽  
Oh Groups ◽  
Neutral Ph ◽  
Carboxylate Groups ◽  
Ph Range ◽  
Phenolic Oh Groups

AbstractThe structure of Np(V) humic acid (HA) complexes at pH 7 was studied by extended X-ray absorption fine structure analysis (EXAFS). For the first time, the influence of phenolic OH groups on the complexation of HA and Np(V) in the neutral pH range was investigated using modified HAs with blocked phenolic OH groups and Bio-Rex70, a cation exchange resin having only carboxyl groups as proton exchanging sites.The formation of Np(V) humate complexes was verified by near-infrared (NIR) spectroscopy. Axial Np-O bond distances of 1.84–1.85 Å were determined for the studied Np(V) humate complexes and the Np(V)-Bio-Rex70 sorbate. In the equatorial plane Np(V) is surrounded by about 3 oxygen atoms with bond lengths of 2.48–2.49 Å. The comparison of the structural parameters of the Np(V) humates with those of Np(V)-Bio-Rex70 points to the fact that the interaction between HA and Np(V) in the neutral pH range is dominated by carboxylate groups. However, up to now a contribution of phenolic OH groups to the interaction process cannot be excluded completely. The comparison of the obtained structural data for the Np(V) humates to those of Np(V) carboxylates and Np(V) aquo ions reported in the literature indicates that humic acid carboxylate groups predominantly act as monodentate ligands. A differentiation between equatorial coordinated carboxylate groups and water molecules using EXAFS spectroscopy is impossible.

scholarly journals Radiation Effects on Pure-Silica Multimode Optical Fibers in the Visible and Near-Infrared Domains: Influence of OH Groups

2021 ◽  
Vol 11 (7) ◽  
pp. 2991
Author(s):  
Cosimo Campanella ◽  
Vincenzo De Michele ◽  
Adriana Morana ◽  
Gilles Mélin ◽  
Thierry Robin ◽  
...  
Keyword(s):  
Optical Fibers ◽  
Radiation Effects ◽  
Near Infrared ◽  
Signal Transmission ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Pure Silica ◽  
Oxygen Hole ◽  
Three Samples ◽  
Radiation Induced

Signal transmission over optical fibers in the ultraviolet to near-infrared domains remains very challenging due to their high intrinsic losses. In radiation-rich environments, this is made even more difficult due to the radiation-induced attenuation (RIA) phenomenon. We investigated here how the number of hydroxyl groups (OH) present in multi-mode (MM) pure-silica core (PSC) optical fibers influences the RIA levels and kinetics. For this, we tested three different fiber samples: one “wet”, one “dry” and one with an intermediate “medium” OH content. The RIA of the three samples was measured in the 400–900 nm (~3 eV to ~1.4 eV) spectral range during and after an X-ray irradiation at a dose rate of 6 Gy(SiO2) s−1 up to a total accumulated dose of 300 kGy(SiO2). Furthermore, we evaluated the H2-pre-loading efficiency in the medium OH sample to permanently improve both its intrinsic losses and radiation response in the visible domain. Finally, the spectral decomposition of the various RIA responses allows us to better understand the basic mechanisms related to the point defects causing the excess of optical losses. Particularly, it reveals the relationship between the initial OH groups content and the generation of non-bridging oxygen hole centers (NBOHCs). Moreover, the presence of hydroxyl groups also affects the contribution from other intrinsic defects such as the self-trapped holes (STHs) to the RIA in this spectral domain.

Near Infrared Spectroscopic Study on the Adsorption of Methanol on Silica Gel

2013 ◽  
Vol 650 ◽  
pp. 150-155
Author(s):  
Alfred A. Christy
Keyword(s):  
Silica Gel ◽  
Infrared Spectra ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Polar Molecules ◽  
Infrared Spectroscopic Study ◽  
Oh Groups ◽  
Glass Vial ◽  
Silanol Groups ◽  
Near Infrared Spectra

The silanol groups on Silica gel surface are sites for adsorption of polar molecules. Alcohols and other polar molecules are easily adsorbed by forming hydrogen bondings with OH groups on silica gel surface. A study on the adsorption of methanol on silica gel was carried out by using NIR spectroscopy in combination with ssecond derivative techniques. Four of the well characterised silica gel samples were used in this study. Each of the silica gel (0.25g) samples with different surface areas and silanol number was pressed into a small disc, placed in a glass vial and the physically adsorbed water molecules from the surface of the silica gel particles were removed by heating the sample to 200 °C under vacuum. The near infrared spectra of the cooled sample was recorded by a Perkin Elmer spectrum one NIR spectrometer equipped with a transflectance accessory and a deuterated triglycine detector at a resolution of 16 cm-1. The glass vial was then opened and a tiny tube filled with methanol was inserted in the glass vial. Then the near infrared spectra of the sample during the adsorption of methanol were recorded at regular time intervals until there is no apparent change in the spectra. The second derivative profiles of the spectra were obtained using the instruments’ software. The mass of the silica gel pellet was determined by an analytical balance and the methanol adsorbed on the surface was calculated. The number of methanol layers on the silica gel surface was calculated using the silica gel particle characteristics of the samples. The results show that the adsorption evolution of methanol progresses on the samples and the surface was covered by a mono layer within the first 60 minutes. Furthermore, it appears that the adsorption of multilayer on methanol starts after all the surface silanol groups are exhausted.

An Application of near Infrared and Mid-Infrared Spectroscopy to the Study of Uranyl Selenite Minerals: Derriksite, Demesmaekerite, Guilleminite and Haynesite

2008 ◽  
Vol 16 (5) ◽  
pp. 455-469 ◽  
Author(s):  
Ray L. Frost ◽  
B. Jagannadha Reddy ◽  
Marilla J. Dickfos
Keyword(s):  
Near Infrared ◽  
Nir Spectroscopy ◽  
Uranyl Ion ◽  
Absorption Feature ◽  
Significant Shift ◽  
Bending Vibrations ◽  
Oh Groups ◽  
Ir Studies ◽  
Geologic Materials ◽  
Bending Modes

The near infrared (NIR) spectra of the natural uranyl selenite minerals that include derriksite, demesmaekerite, guilleminite and haynesite are examined as a potential indicator of uranium occurring geologic materials at the earth's surface. NIR analysis, complimented with mid-IR studies, was used to investigate the co-ordination of UO22+ and Cu2+ in the uranyl selenites. Bands obtained from the infrared spectra of selenites are interpreted in terms of the stretching vibrations of uranyl, selenite units and OH groups and bending modes. NIR spectra of the uranyl selenite minerals exhibit distinctive characteristics of uranyl ion (UO2)2+ absorptions over the range of 11,500–8000 cm−1. The high- range NIR spectrum of Cu-bearing uranyl derriksite is resolved into two bands, UO22+ 8070 cm−1 and Cu2+ 7175 cm−1. The effect of lead in demesmaekerite leads to distortion of the spectrum and the NIR bands are observed for uranyl ion at 11,305 cm−1 and 8475 cm−1 and for Cu2+ at 7430 cm−1. The δ U–OH bending vibrations are characterised by a strong absorption feature centred at 1015 cm−1 in haynesite. A significant shift for UOH bending vibrations and the absence of ν1 and ν3 vibrations of UO22+ at the expense of Cu2+ are reflected in the spectrum of derriksite. The complexity of bands with shifts to low wavenumbers could take place due to the additional cations of Pb and Cu in the structure of demesmaekerite. NIR spectroscopy has proven to be a most useful tool for the identification of and distinction between different uranyl selenite minerals.

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