Solid-state Fourier Transform Infrared Research Articles

Secondary Metal Coordination Using a Tetranuclear Complex as Ligand Leading to Hexanuclear Complexes with Enhanced Thermal Barriers for Electron Transfer

Postsynthesis of the paramagnetic square-shaped complex {[(Tp*Me)Fe(μ-CN)2(CN)][Co(dmbpy)2]}2(BPh4)2·6MeCN·H2O [1, Tp*Me = tris(3,4,5-trimethylpyrazole)-borate; dmbpy = 4,4′-dimethyl-2,2′-bipyridin...

Chemical structure changes of lacustrine Type-II kerogen under semi-open pyrolysis as investigated by solid-state 13C NMR and FT-IR spectroscopy

At present, there is a lack of research on the structural changes of lacustrine Type-II kerogen, which is regionally distributed but has significant potential for hydrocarbon resources. In our previous work, a series of non-hydrous, temperature-based semi-open pyrolysis experiments have been performed on the Chang 7 oil shale to simulate the thermal maturation (from 0.53 %Ro to 1.68 %Ro) of lacustrine Type-II kerogen. In that work, the parallel reaction pathway for kerogen decomposition was supported. The aim of this work is to reveal the structural changes of the post-pyrolysis kerogen. Integrated analysis including elemental analysis, programmed pyrolysis (Rock-Eval), Fourier transform infrared (FT-IR) spectroscopy, and solid-state 13 C nuclear magnetic resonance ( 13 C NMR) spectroscopy were conducted on the native unheated and post-pyrolysis rocks and kerogens. Based on the compositional features of the hydrocarbon products, structural changes of the post-pyrolysis kerogen were investigated, and insights on the initial chemical structure of the kerogen were also obtained. Before the peak hydrocarbon-generating stage ( R o < 0.6%), defunctionalization of oxygen-containing functional groups, which leads to the generation of water, CO 2 and NSOs, occurs simultaneously with the detachment of short aliphatic side chains and small aromatic rings, which leads to the generation of volatile fractions (C 6 –C 14 , C 15+ sat and C 15+ aro). This process suggests that the Chang7 kerogen is highly branched. During the peak hydrocarbon-generating stage (0.6–1.09 % R o ), the concurrent breakage of weak cross-link bonds and long aliphatic chains lead to the simultaneous peak generation of liquid hydrocarbons and NSOs. This reflects the highly cross-linked features of the Chang7 kerogen. After the peak hydrocarbon-generating stage ( R o > 1.09%), the reactions in the previous two stages produce a highly aromatic kerogen. The increased aromaticity of the highly matured kerogen is most likely to be caused by aromatization or dehydrogenation of hydroaromatics and coking of aromatic bitumen, not by fusing or condensation of aromatic rings. • Chemical structural evolution of Chang7 lacustrine Type-II kerogen was characterized for the first time. • Kerogen reached artificial maturation under non-hydrous, temperature-based semi-open pyrolysis experiments. • Parallel bond breaking mechanism of unusual lacustrine Type-II kerogen was supported from chemical structure changes.

Effect of the Ratio of Acetylacetate Groups on the Properties of a Novel Plant-Based Dual-Cure Coating System.

A novel plant-based dual-cure coating system based on a Michael addition reaction between bismaleimide (BDM) and modified acetoacetylated castor oil was developed. The BDM has a high reactivity toward acetylacetate groups, and the catalyst 1,4-diazabicyclo[2.2.2]octane (TEDA) was optimized by the rheological viscosity. The gel was characterized by Fourier transform infrared (FTIR) spectroscopy. Then, three films were prepared with the TEDA catalyst and analyzed with solid-state 13C NMR and FTIR spectroscopy. The thermal and mechanical properties of the three films were characterized by differential mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry. We found that the cross-linking density, glass transition temperature (Tg), and Young’s modulus of the coating films increased with an increase in the ratio of acetylacetate groups from the modified acetoacetylated castor oil. This is the first study of the reaction of BDM with plant-based acetylacetate groups. Importantly, a quantitative ratio of acetylacetate groups can be obtained by a thiol–ene coupling reaction and a transesterification reaction, resulting in the formation of films having excellent performance.

Tannin-Based Copolymer Resins: Synthesis and Characterization by Solid State 13C NMR and FT-IR Spectroscopy.

In recent years, the interest for bio-sources is rising exponentially and tannins extracts are one of the most interesting, easily-available, phenolic building blocks. The condensed tannins or proanthocyanidins are already known for their polymerization chemistry, which is the basis for several natural-based materials (e.g., adhesives, foams). In the present work we aim to observe the behavior of the extract of Acacia Mimosa (Acacia mearnsii) when reacted with several possible co-monomers at different relative amount, pH and temperature conditions. The more insoluble copolymers obtained with formaldehyde, hexamine, glyoxal, maleic anhydride, furfural and furfuryl alcohol were analyzed through solid state 13C NMR (Nuclear magnetic resonance) and FT-IR (Fourier Transform-Infrared) spectroscopy. The 13C NMR afforded the opportunity to detect: (i) aromatic substitutions and consequent poly-condensations for the majority of the hardeners studied; (ii) acylation for the maleic anhydride and also some; (iii) Diels–Alder arrangements for the furanic co-monomers; the FT-IR spectroscopy suggested that the formaldehyde and hexamine copolymers present a higher cross-linking degree.

Extraction and thermal dissolution of Piliqing subbituminous coal

Piliqing subbituminous coal (PSBC) was exhaustively extracted with isometric acetone/carbon disulfide mixed solvent under ultrasonic irradiation to afford extractable portion (EP) and extraction residue (RE). Then RE was subjected to sequential thermal dissolution (TD) in ethanol at 200, 240, 280, and 320°C and TD at each temperature was conducted for 2h. The sequential TD provided soluble portions (SPs) 1–4 (SP1–SP4) and residue 4 (R4). EP and the SPs were analyzed with a gas chromatograph/mass spectrometer and Fourier transform infrared (FTIR) spectrometer, while PSBC, RE, and R4 were characterized with a solid-state 13C nuclear magnetic resonance (SS 13C NMR), FTIR, and X-ray photoelectron spectrometer (XPS). In total, ca. 36wt% of organic matter was released from PSBC by the ultrasonic extraction and sequential TD. EP is rich in normal alkanes and arenes, while dialkoxyalkanes are predominant in SP1 and esters are the main compounds in SP2–SP4. No significant difference in the distribution of functional groups was observed in FTIR spectra of PSBC and RE, while the distribution of functional groups in R4 is significantly different from that in either PSBC or RE. According to analysis with XPS, the content of oxygen-containing species in R4 is relatively low. PSBC consists of 32.6% aliphatic carbon atoms, 63.0% aromatic carbon atoms, and 4.4% carbonyl carbon atoms, while the content (2.0%) of carbonyl carbon atoms in R4 is significantly lower than that (4.4%) in PSBC based on analysis with SS 13C NMR.

Cysteine-montmorillonite composites for heavy metal cation complexation: A combined experimental and theoretical study

Green composites based on montmorillonite (Mt) and cysteine, were prepared for heavy metal removal. A comparison between the adsorption properties of the resulting hybrid inorganic-organic materials and the pure montmorillonite was carried out for the following heavy metal cations Cd2+, Hg2+, Pb2+, Co2+ and Zn2+. It appears that the adsorption capacity is higher on the composite. Moreover, in release experiments, the heavy metal cations are more strongly retained by the hybrid material. Interactions between the hybrid clay mineral and the inorganic hosts were studied by spectroscopic methods such as solid-state NMR (Nuclear Magnetic Resonance) and FTIR (Fourier Transform Infrared). The experimental data were in agreement with the theoretical periodic DFT (Density Functional Theory) calculations where a molecular picture of the adsorption complex is proposed.

Weathering characteristics of bamboo (Phyllostachys puberscence) exposed to outdoors for one year

The 1–3-year-old bamboo (Phyllostachys puberscence) culms were exposed to ambient weathering conditions for 12 months. Changes in color, surface topography, and chemical features of bamboo culms by weathering were investigated. Changes in the surface color of culms increased sharply in the first 3 months weathering and then slowly decreased compared to control culms. Surface checks developed more markedly in the 2- and 3-year-old bamboos than in the 1-year-old ones. The depth of erosion was extended up to 150 µm from the outer surface of culms. Solid-state NMR (nuclear magnetic resonance) and FT-IR (Fourier transform infra-red) spectra showed that the lignin and hemicelluloses of bamboo culms were preferentially affected by natural weathering, while crystalline cellulose remained relatively intact.

Solid-state NMR and FTIR studies of lime stabilized montmorillonitic and lateritic clays

The poor engineering properties of soils containing high amounts of clay minerals can be altered through chemical stabilization, resulting in a material suitable for geotechnical applications. The primary objective of this research was to study the time-dependent changes in the structure of lime stabilized montmorillonitic and lateritic clays using solid state nuclear magnetic resonance (SS-NMR) and Fourier transform infrared (FTIR) spectroscopy. The 29Si and 27Al MAS NMR spectra of montmorillonite dominated soils indicated that the reaction products of the attack on the tetrahedral sheets were mainly responsible for the formation of new composites that bound the soil particles together. Furthermore, the coating of iron (hydr)oxides on the surface of the laterite clay particles retarded the pozzolanic reactions. The presence of lime in the soil-stabilizer matrix was also confirmed by a new band observed in the FTIR spectra. From the geotechnical point of view, the lime treated bentonite showed the highest degree of improvement with an approximately 11-fold strength increase in comparison to the natural soil within 8-month curing periods.

Induced Secondary Structure and Polymorphism in an Intrinsically Disordered Structural Linker of the CNS: Solid-State NMR and FTIR Spectroscopy of Myelin Basic Protein Bound to Actin

The 18.5 kDa isoform of myelin basic protein (MBP) is a peripheral membrane protein that maintains the structural integrity of the myelin sheath of the central nervous system by conjoining the cytoplasmic leaflets of oligodendrocytes and by linking the myelin membrane to the underlying cytoskeleton whose assembly it strongly promotes. It is a multifunctional, intrinsically disordered protein that behaves primarily as a structural stabilizer, but with elements of a transient or induced secondary structure that represent binding sites for calmodulin or SH3-domain-containing proteins, inter alia. In this study we used solid-state NMR (SSNMR) and Fourier transform infrared (FTIR) spectroscopy to study the conformation of 18.5 kDa MBP in association with actin microfilaments and bundles. FTIR spectroscopy of fully 13C, 15N-labeled MBP complexed with unlabeled F-actin showed induced folding of both protein partners, viz., some increase in β-sheet content in actin, and increases in both α-helix and β-sheet content in MBP, albeit with considerable extended structure remaining. Solid-state NMR spectroscopy revealed that MBP in MBP-actin assemblies is structurally heterogeneous but gains ordered secondary structure elements (both α-helical and β-sheet), particularly in the terminal fragments and in a central immunodominant epitope. The overall conformational polymorphism of MBP is consistent with its in vivo roles as both a linker (membranes and cytoskeleton) and a putative signaling hub.

Self-Assembly, Optical, and Mechanical Properties of Surfactant-Directed Biphenyl-Bridged Periodic Mesostructured Organosilica Films with Molecular-Scale Periodicity in the Pore Walls

Self-assembly, optical, and mechanical properties of surfactant-directed biphenyl-bridged periodic mesoporous organosilica thin films (PMOF-Bp's) with molecular-scale periodicity in the pore walls were successfully demonstrated for the first time. The biphenyl-bridged organosilica precursor, 4,4-bis(triethoxysilyl)biphenyl (Bp-TES) has been used as the sole precursor (100%) for preparing PMOF-Bp films with molecular-scale periodicity in the pore walls via the surfactant-mediated one-step mild acidic self-assembly process. High-resolution X-ray diffraction (HRXRD) patterns and transmission electron microscope (TEM) images of PMOF-Bp materials confirmed the formation of a biphenyl-bridged periodic mesophase with molecular-scale periodicity in the organosilica framework. Fourier transform infrared (FT-IR) and NMR spectroscopic data also strongly suggested that the biphenyl organic segment is covalently bonded with silicon atoms in the acidic ethanol-washed biphenyl-bridged mesoporous framework. The emission behavior is sensitive to synthesis and thermal treatment temperatures. The biphenyl-bridged PMO films show absorption and emission due to the presence of biphenyl segment in pore walls. Nanoindentation hardness of the PMOF-Bp films could be controlled by temperature, degree of pore ordering and molecular periodicity, and even thickness of films. For example, well-organized PMOF-Bp film with molecular-scale periodicity in the pore walls showed a higher hardness value (0.23 GPa) than that of less mesoordered PMOF-Bp film (0.13 GPa). For all solvent-extracted PMO samples, N(2) gas sorption experiments showed the surface area (from 714 to 688 m(2)/g), the pore volume (from 0.76 to 0.68 cm(3)/g), and pore size (2.81 to 3.1 nm). The solid-state NMR and FT-IR spectroscopic data were used to propose plausible interpretations of the formation of hydrogen-bonded molecular periodicity in the pore walls. The experimental periodicity value 1.40 nm was strongly supported by the periodicity obtained by the structural model (1.389 nm).

Direct Synthesis and Characterization of Amine-Functionalized Mesoporous Silica Materials and Their Applications as Formaldehyde Adsorbents

Amine-functionalized mesoporous materials were tailored through co-condensation of tetraethoxysilane and n-(2-aminoethyl)-3-aminopropyltrimethoxysilane varied in a range of 0–50 mol% in the presence of cetyltrimethyl ammonium bromide as template. Materials were characterized for textural properties by nitrogen adsorption methods and transmission electron microscopy (TEM) and chemical structure by Fourier transform infrared (FTIR) and silicon-29 nuclear magnetic resonance (29Si-NMR) spectroscopies. Adsorptive capacity for gaseous formaldehyde was also investigated, using a desiccator method. Adsorption data was fit using Langmuir, Freundlich, and Temkin isotherms. BET surface area results showed the effect of n-(2-aminoethyl)-3-aminopropyltrimethoxysilane loading. As the concentration of n-(2-aminoethyl)-3-aminopropyltrimethoxysilane was increased, lower BET surface area was obtained. High concentration of n-(2-aminoethyl)-3-aminopropyltrimethoxysilane added into the initial mixture resulted in reduced surface area and pore volume. Solid-state NMR and FTIR demonstrated the incorporation of amine functional groups on pore walls of the amine-functionalized materials. In addition, FTIR spectra indicated that the amine site on pore surfaces reacted with formaldehyde during adsorption and showed that the surfactant template can be removed from silica matrix using an extraction method. Formaldehyde adsorption was well described by a Langmuir isotherm. The capacity of the adsorbent mainly depended on the amount of amine groups on the pore surface. Materials derived from 80 mol% of tetraethoxysilane and 20 mol% of n-(2-aminoethyl)-3-aminopropyltrimethoxysilane had lower surface area than that of the pure mesoporous silica adsorbent and shows the highest adsorptive capacity, which is around two times higher than that of the pure mesoporous silica.

New copper(II) complexes of polyampholyte and polyelectrolyte polymers: Solid-state NMR, FTIR, XRPD and thermal analyses

Novel solid copper(II) complexes were obtained from the polyampholyte poly(EGDE–MAA–IM) and the polyelectrolyte poly(EGDE–MAA) polymers with copper salts at different concentration levels.The materials were characterized employing solid-state Nuclear Magnetic Resonance (NMR), Fourier Transform infrared (FTIR), X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and thermogravimetry (TG).The reticulation induced by MAA in these materials against the poly(EGDE–IM) gel was analyzed by DSC. The coordination behavior of the carboxylic acid of MAA, compared to that provided by the imidazole ring, was studied through solid-state 13C NMR and changes in the FTIR spectra. The non-homogenous character of the doped and undoped materials was analyzed by the glass transition temperature (Tg), 2D 1H–13C WISE NMR and proton spin–lattice relaxation time in the rotating frame (TH1ρ). In particular, the TH1ρ and TH1 values in the complexes decreased with the Cu(II) concentration, showing the high sensitivity of both parameters to the presence of a paramagnetic ion. Finally, the thermogravimetric studies indicated that the presence of the imidazole ring was decisive for the stability of the Cu(II) complexes and for the undoped polymers.

Multivariate Chemometric Approach to Thermal Solid-State FT-IR Monitoring of Pharmaceutical Drug Compound

The study of thermal-related solid-state reaction monitored by spectroscopic method needs the use of advanced multivariate chemometric approach. It is because visual inspection of spectral data on particular functional groups or spectral bands is difficult to reveal the complete physical and chemical information. The spectral contributions from various species involved in the solid-state changes are generally highly overlapping and the spectral differences between reactant and product are usually quite minute. In this article, we demonstrate the use of multivariate chemometric approach to resolve the in situ thermal-dependent Fourier-transform infrared (FT-IR) mixture spectra of lisinopril dihydrate when it was heated from 24 to 170 degrees C. The collected FT-IR mixture spectra were first subjected to singular value decomposition (SVD) to obtain the right singular vectors. The right singular vectors were rotated into a set of pure component spectral estimates based on entropy minimization and spectral dissimilarity objective functions. The resulting pure component spectral estimates were then further refined using alternating least squares (ALS). In current study, four pure component spectra, that is, lisinopril dihydrate, monohydrate, anhydrate, and diketopiperazine (DKP) were all resolved and the relative thermal-dependent contributions of each component were also obtained. These relative contributions revealed the critical temperature for each transformation and degradation. This novel approach provides better interpretation of the pathway of dehydration and intramolecular cyclization of lisinopril dihydrate in the solid state. In addition, it can be used to complement the information obtained from differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Influence of animal manure application on the chemical structures of soil organic matter as investigated by advanced solid-state NMR and FT-IR spectroscopy

Annual application of cattle manure to a farmer's field in eastern Nebraska for 5 yr caused improved soil N and P supply and increased corn ( Zea mays L.) yield in less productive portions of the field compared to another field treatment receiving the same amount of N as inorganic fertilizer. As a first step toward identifying the soil processes that led to these changes, the effects of manure addition on the chemical nature of soil organic matter were investigated by extracting two humic fractions—mobile humic acid (MHA) and calcium humate (CaHA)—from the field soil for subsequent analysis by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and Fourier Transform-infrared (FT-IR) spectroscopy. Functional groups were selectively identified and quantified through NMR techniques that included quantitative direct polarization, cross polarization/total suppression of sidebands, 1H- 13C heteronuclear correlation NMR, 13C chemical shift anisotropy filtering, CH-signal selection, and other spectral-editing techniques. The CaHAs exhibited high aromaticity and line shapes typical of Mollisols rich in oxidized charcoal, while the MHAs had lower aromaticity and greater contributions from lignin aromatic ethers. Results show that the chemical nature of each humic fraction did not differ significantly between an unfertilized control and the treatment receiving N as inorganic fertilizer. The FT-IR results were consistent with all these findings. The NMR results further showed that the CaHA fraction from the manure treatment was clearly depleted in aromatic rings and enriched in nonpolar alkyl compounds, most likely fatty acids, compared to the other two fertilizer treatments. Selective spectra further show strong indications of enhanced peptide contributions in the manure CaHA, consistent with the improved soil N supply associated with the manure treatment. The peptide enrichment was partially masked in unselective spectra by a simultaneous decrease in overlapping signals for OCH 3 and COO groups that are associated with aromatic components, demonstrating the improved accuracy of the selective spectral-editing NMR techniques.

Structural characterization of kerogen in 3.4 Ga Archaean cherts from the Pilbara Craton, Western Australia

Hydrogen-lean kerogen (atomic H/C < 0.46) isolated from the 3.4 Ga Strelley Pool Chert in the North Pole area, Pilbara Craton, Western Australia, were studied by vibrational spectroscopy (Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy), nuclear magnetic resonance spectroscopy (solid state 13C NMR spectroscopy), catalytic hydropyrolysis followed by gas chromatography mass spectrometry (HyPy–GC–MS), and isotope ratio mass spectrometry (IRMS). The kerogen occurs in sedimentary rocks as clasts and clots deposited together with other detrital materials that are finely disseminated throughout a chert matrix. The bulk kerogen δ 13C values range from −28.3 to −35.8‰. Solid-state 13C NMR spectroscopy and FTIR spectroscopy reveals that the kerogen is highly aromatic ( f a varying from 0.90 to 0.92) and contains only minor aliphatic carbon or carbon-oxygenated (C–O) functionalities. The Raman carbon first-order spectra for the isolated kerogens are typical of spectra obtained from disordered sp 2 carbons with low 2-D ordering (biperiodic structure). The implications of the Raman results show low 2-D ordering throughout the carbonaceous network indicate the incorrect usage of the term graphite in the literature to describe the kerogen or carbonaceous material in the Warrawoona cherts. Hydropyrolysates contain aromatic compounds consisting of 1-ring to 7-ring polycyclic aromatic hydrocarbons which were covalently bound into the kerogen as well as alkanes (linear, branched and cyclic) which were most probably trapped in the microporous network of the kerogen. These PAHs have mainly C1- and C2-alkylation while C 3+-substitued aromatics are low in abundance and do not show a high degree of branched alkylation. For the first time we have shown a correlation between elemental analysis (H/C atomic ratios), Raman spectroscopic parameters ( I D1/ I G, I D1/( I D1 + I G), and L a), and the degree of alkylation of bound polyaromatic molecular constituents generated from HyPy for Archaean kerogens. Similarities in molecular profiles exist between HyPy products of Strelley Pool Chert kerogens and an oil-window-mature Mesoproterozoic kerogen from Roper Group (ca. 1.45 Ga), which is biogenic in origin, suggesting that the Strelley Pool Chert kerogens may also be derived from diagenesis and thermal processing of biogenic organic matter. A combination of Raman spectroscopy, for identifying the least metamorphosed kerogens, used together with HyPy for liberating trapped and bound molecular components of these kerogens, offers a powerful strategy for assessing the origins of Earth's oldest preserved organic matter.

Characterization of Local Structures in Flexible Polyurethane Foams by Solid-state NMR and FTIR Spectroscopy

The article examines the characterization of local structures in water-blown flexible polyurethane foams with various amine catalysts. In this study, the authors have applied solid-state nuclear magnetic resonance (NMR) relaxation, nuclear spin diffusion, and Fourier transform infrared (FTIR) microscope analysis on flexible polyurethane foams. Quantitative knowledge of the polymer structure and dynamics by these methods provides a significant insight on understanding the microphase separation and the domain structure of urethane and urea hard segments and polyether soft segments in foam. Furthermore, the authors analyze the influence of hydrothermal degradation on the microphase structure of the foams. A detailed comparison of the fundamental results with conventional foam durability tests (e.g., humid aged compression sets) is described, and the hydrothermal degradation mechanism and the influence of catalysts on the foam stability are discussed.

Fluorescence excitation-emission matrix regional integration to quantify spectra for dissolved organic matter.

Excitation-emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the > 10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation-emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation-emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (phi(i,n)). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet-visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 hydrophobic or hydrophilic acid, neutral, and base DOM fractions plus nonfractionated DOM from wastewater effluents and rivers in the southwestern United States. DOM fractions fluoresced in one or more EEM regions. The highest cumulative EEM volume (phi(T,n) = sigma phi(i,n)) was observed for hydrophobic neutral DOM fractions, followed by lower phi(T,n) values for hydrophobic acid, base, and hydrophilic acid DOM fractions, respectively. An extracted wastewater biomass DOM sample contained aromatic protein- and humic-like material and was characteristic of bacterial-soluble microbial products. Aromatic carbon and the presence of specific aromatic compounds (as indicated by solid-state 13C NMR and FTIR data) resulted in EEMs that aided in differentiating wastewater effluent DOM from drinking water DOM.

Miscibility Behavior and Specific Interaction of Phenolic Resin with Poly(acetoxystyrene) Blends

Full Paper: The miscibility behavior and specific interaction of phenolic resin with poly(acetoxystyrene) (PAS) blends were examined using differential scanning calorimetry (DSC), fourier-transform infrared (FT-IR) spectroscopy and solid-state NMR. This phenolic/PAS blend is fully miscible, as indicated by a single glass-transition temperature, due to the formation of inter-hydrogen bonding between the hydroxyl group of the phenolic resin and the carbonyl group of PAS. The DSC study indicates that this phase-separation exothermic peak area is closely related to the interaction between the components. Furthermore, 13 C solid-state NMR and FT-IR spectroscopies were used to study the extent of specific interaction with various compositions and degrees of inter- and intramolecular hydrogen bonding. Moreover, the inter-association equilibrium constant and the related enthalpy of this phenolic/PAS blend were determined and used to predict the free energy and fraction of the hydrogen bonding according to the Painter‐Coleman association model.

Nuclear magnetic resonance and infrared spectroscopic analysis of nedocromil hydrates.

Nedocromil sodium (NS), which is used in the treatment of reversible obstructive airway diseases, such as asthma, has been found to exist in the following solid phases: the heptahemihydrate, the trihydrate, a monohydrate, an amorphous phase, which contains variable amounts of water, and a recently discovered methanol + water (MW) solvate. Our aim was to apply 13C solid-state nuclear magnetic resonance (NMR) spectroscopy and solid-state Fourier transform infrared (FTIR) spectroscopy to the study of specific interactions in the various solid forms of NS. The 13C solid-state NMR and FTIR spectra of the various solid forms of NS were obtained and were related to the crystal structures of NS, the conformations of the nedocromil anion, and the interactions of the water molecules in these crystals. The 13C solid-state NMR spectrum is sensitive to the conformation of the nedocromil anion, while the solid-state FTIR spectrum is sensitive to interactions of water molecules in the solid state. In NS monohydrate, for which the crystal structure has not yet been solved, and in the amorphous phase, the information about the conformations of the nedocromil anion and the interactions of the water molecules are deduced from the 13C solid-state NMR spectra and solid-state FTIR spectra, respectively. 13C solid-state NMR spectroscopy and solid-state FTIR spectroscopy are shown to be powerful complementary tools for probing the chemical environment of molecules in the solid state, specifically the conformation of the nedocromil anion and the interactions of water-molecules, respectively.

Solid-state NMR and FTIR studies on bilayer membranes from 1,2-dioctadec-(14-ynoyl)- sn-glycero-3-phosphatidylcholine

Multilamellar dispersions from a new model phospholipid, 1,2-dioctadec-(14-ynoyl)- sn-glycero-3-phosphatidylcholine (DO(14-yne)PC), bearing a triple bond in the fatty acid chains are studied by 2H, 31P NMR and Fourier transform infrared (FTIR) spectroscopy. The investigations are focused on the evaluation of the molecular properties of the lipid molecules as function of temperature and sample composition. Information about the fatty acid chain conformations are obtained from FTIR measurements by analysing the CH 2 wagging and stretching modes. 2H NMR studies are performed on two selectively deuterated compounds that provide further insights into the molecular characteristics at two specific positions along the fatty acid chains. These studies demonstrate that the introduction of the triple bond is accompanied by a reduction of fatty acid chain order which holds for both the conformational and the orientational order. Likewise, 31P NMR spectroscopy is used for the determination of the dynamics and ordering in the head group region. Here, particular emphasis is given to the evaluation of the lipid lateral motions that are quantified over a large temperature range within the liquid crystalline phase. It is found that the lateral mobility of the lipid molecules is almost unaffected by the triple bond in the fatty acid chains. The addition of cholesterol gives rise to a reduction in lateral mobility for DO(14-yne)PC, as can be followed by spin echo, 2D-exchange NMR and stimulated echo experiments.