13C Nuclear Magnetic Resonance Spectroscopy Research Articles

Carbonate-Terminated Self-Assembled Monolayers for Mimicking Nanoscale Polycarbonate Surfaces

Two carbonate-terminated alkanethiol molecules having different positional isomers of a six-membered cyclic carbonate group, 3-COC12SH and 2-COC12SH, were synthesized and used to generate self-assembled monolayers (SAMs) on gold to serve as mimics of the surfaces of commercially available poly(propylene carbonate) (PPC) and poly(ethylene carbonate) (PEC). The adsorbate molecules were characterized using 1H and 13C nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. The corresponding SAMs on gold were characterized by ellipsometry, contact angle goniometry, polarization-modulation infrared reflection-adsorption spectroscopy, and X-ray photoelectron spectroscopy. The contact angle data showed that the wettabilities of both SAMs were largely similar to each other and to the PEC samples for a wide range of contacting probe liquids (with water correlating particularly well with PEC and both SAMs). As a whole, the wettability data suggest that the carbonate-terminated SAMs can serve as mimics of nanoscale polycarbonate surfaces and can be used to investigate the interfacial properties of polycarbonates without interference from the surface reconstruction.

Design, synthesis and antifungal activities of novel cis-enamides via intermediate derivatization method

On the basis of the structure of natural product lansiumamide B (1), a total of 27 novel cis-enamide compounds were designed and synthesized via Intermediate Derivatization Method. Their chemical structures were characterized by 1H and 13C nuclear magnetic resonance and high-resolution mass spectrometry. The in vitro antifungal activities against Sclerotinia sclerotiorum, Thanatephorus cucumeris and Botrytis cinerea were evaluated by the mycelium linear growth rate method. Most of the compounds showed some activity against each of the fungi at 25 or 50 μg/mL. The relationship between structure and antifungal activity was also discussed, which showed the cinnamic double bond was critical to maintain the antifungal activity. Notably, among the title compounds, 3e and 3h could inhibit mycelia growth of Botrytis cinerea by approximately 50% (EC50) at 39.17 and 41.25 μg/mL respectively, which showed better antifungal activity than lansiumamide B (1) with more concise chemical structure. The present study pointed out the correct direction for the development and optimization of lansiumamide B derivatives as potential inhibitors of pathogenic fungi.

Via conformational flexibility, triglycerides stabilize organic-water interfaces of changing area.

The role of triglycerides (TGs) in both synthetic and biological membranes has long been the subject of study, involving metabolism, disease, and colloidal synthesis. TGs have been found to be critical components for successful liposomal encapsulation via double emulsion (Water/Oil/Water), which this work attempts to explain. TGs can occupy multiple positions in a biological membranes. The glycerol backbone can sit at the membrane's interface with water, adjacent to phospholipid headgroups (“surface” or “M” conformation), typically with relatively low (∼3%) solubility. TGs can also occupy “oil” phases, where the glycerol backbone is isolated from water, in either mid-membrane positions or lipoprotein-style phospholipid-coated TG droplets. Using 13C-Nuclear magnetic resonance spectroscopy (NMR) to determine the degree of hydration of the TG backbone, it was revealed that TGs transition from surface to oil phases as the organic solvent is removed via evaporation. A new, transitional TG backbone position has been identified, with a level of hydration between surface and oil. These results suggest that TGs are able to temporarily coat and stabilize the large water/organic interfaces present just after emulsification. As the chloroform evaporates and interfaces shrink, the TGs recede into mid-membrane spaces or to bud off into separate coated oil droplets, which are confirmed via transmission electron microscopy. These TG-rich droplets can be removed via high-speed centrifugation. Encapsulation efficiency is found to be inversely related to both chain saturation and length, indicating that membrane fluidization is a key property arising from the presence of TGs. Beyond clarification of a mechanism for high-efficiency liposomal encapsulation, these results implicate TGs as components that are able to stabilize biological membrane transitions involving changing interfacial area. This role for TGs may be of use in designing drug delivery systems and investigation of membrane transitions in life sciences.

A Study on the Behavior of Cadmium in the Soil Solution-Plant System by the Lysimeter Method Using the 109Cd Radioactive Tracer.

In soils, cadmium (Cd) and its compounds, originating from industrial activities, differ both in mobility as well as in their ability to permeate the soil solution from naturally occurring cadmium compounds (native Cd). Therefore, the determination of the parameters of cadmium mobility in soils and its accumulation by plants in the soil-soil solution-plant system is very important from both scientific and practical viewpoints. 109Cd was used as a radioactive tracer to study the processes of the transition of Cd into the aqueous phase and its uptake by plants over the course of a vegetative lysimeter experiment. Using sequential extraction according to the Tessier-Förstner procedure and modified BCR schemes, certain patterns were determined in the distribution of Cd/109Cd among their forms in various compounds in the soil, along with the coefficients of the enrichment of native stable Cd with radioactive 109Cd. It was shown that the labile pool of stable Cd compounds (29%) was significantly smaller than that of radioactive 109Cd (69%). The key parameters characterizing the migration capacity of Cd in the soil-soil solution-plant system were determined. It was found that the distribution coefficient of native Cd between the soil and the quasi-equilibrium lysimeter solution exceeded the similar value for the 109Cd radionuclide by 2.2 times, and the concentration coefficients of Cd and 109Cd in the barley roots were 9 times higher than in its vegetative parts. During the experiment, the average removal of Cd (109Cd) from the soil by each barley plant was insignificant: 0.002 (0.004)%. Based on the results of 13C nuclear magnetic resonance (NMR) spectroscopy of a lyophilized sample of the high-molecular-weight dissolved organic matter (HMWDOM) of the soil solution, its components were determined. It transpired that the isolated lyophilized samples of HMWDOM with different molecular weights had an identical structural and functional composition. The selective sorption parameters of the HMWDOM and humic acid (HA) with respect to Cd2+ ions were determined by the isotope dilution method.

Synthesis, characterization and anti-breast cancer activity of some maleimide derivatives

This study included the synthesis of four compounds of maleimide derivatives. Novel compounds (K1-K4) resulted from the reaction between N-substituted maleimide and aryl hydrazide (benzohydrazide, p-toluic hydrazide or isonazide). The novel maleimide derivatives were identified using infrared spectroscopy (FT-IR), 1H- and 13 C-nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry, as well as the melting point of the preparing compounds. The MTT assay were used to examine the anti-breast cancer (MCF-7) activities of four compounds. The compounds K2 and K4 demonstrated anti-cancer activity against breast cancer cells.

Synthesis, Characterization and Thermal Properties of Photoresponsive Epoxy Resin Containing Benzylidene Units in the Main Chain


 Abstract
 A photoresponsive epoxy resin containing benzylidene units in the main chain has been prepared from bis (4-hydroxybenzylidene) cyclohexanone and epichlorohydrin using solution polycondensation method. The resulting compound possessed both the oxirane ring and benzylidene units. Thus, it has been highlighted in practical applications. The chemical structure of epoxy resin was characterized by Fourier transform infrared (FT-IR) and (1H, 13C) nuclear magnetic resonance (NMR) spectroscopies. The photolysis via [2π + 2π] cycloaddition reaction of the epoxy resin in the chloroform solution was studied by the UV-irradiation (350 nm). The thermal properties results show that the resulting epoxy resin is stable until 350 °C and its glass transition temperature is about 140 °C, which they were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively, to demonstrate its potential in the industrial coatings. 
 

Steric hindrance affects interactions of poly(styrene–alt–DMHPMI) copolymer with strongly hydrogen-bond-accepting homopolymers

In this study, we synthesized the monomer N-(2,6-dimethylhydroxyphenyl)maleimide (DMHPMI) in three steps from 2,6-dimethylphenol and then reacted it with styrene through free radical copolymerization to prepare the alternating copolymer poly(styrene–alt–dimethylhydroxyphenylmaleimide) [poly(S–alt–DMHPMI)]. We used Fourier transform infrared (FTIR) spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and mass-analyzed laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry to confirm its structure. Differential scanning calorimetry revealed that blends of the alternating copolymers poly(S–alt–DMHPMI) and poly(styrene–alt–(para–hydroxyphenylmaleimide)) [poly(S–alt–pHPMI)] with the Strongly Hydrogen-Bond-Accepting homopolymers poly(4-vinylpyridine) (P4VP) and polyvinylpyrrolidone (PVP) each exhibited single-value glass transition temperatures (Tg) over the entire compositional range, indicative of full miscibility. Nevertheless, a negative deviation from the linear rule occurred for the Tg behavior of the PS–alt–PHPMI/P4VP blends, due to the weak acidity of the HPMI units, while the intermolecular interactions of the PS–alt–PHPMI coplymers were also inhibited because of strong self-association of the PHPMI units. FTIR spectral analyses of the ratio of hydrogen-bonded OH and pyridyl groups confirmed this behavior. In contrast, slightly positive deviations from the linear rule occurred for the Tg behavior when blending poly(S–alt–DMHPMI) or poly(S–alt–pHPMI) with the PVP homopolymer; here, the intermolecular interactions of the poly(S–alt–DMHPMI)/PVP blends were weaker than those of the poly(S–alt–pHPMI)/PVP blends, due to the steric hindrance of the DMHPMI units being greater than that of the pHPMI units.

Structural Characterization and Hypoglycemic Function of Polysaccharides from Cordyceps cicadae.

The polysaccharides isolated and purified from different parts of the medicinal fungus Cordyceps cicadae were identified, and three extracts displaying significant biological activities were selected for further study. The bacterium substance polysaccharides (BSP), spore powder polysaccharides (SPP), and pure powder polysaccharides (PPP) were separated, purified, and collected from the sclerotia, spores, and fruiting bodies of Cordyceps cicadae, respectively. The structures of Cordyceps cicadae polysaccharides were analyzed using gas chromatography, Fourier-transform infrared spectroscopy, methylation analysis, and one-dimensional (1H and 13C) nuclear magnetic resonance spectroscopy. Moreover, the hypoglycemic effect of Cordyceps cicadae polysaccharides was examined in both in vitro and in vivo models. BSP, SPP, and PPP significantly increased glucose absorption in HepG2 cells, and alleviated insulin resistance (IR) in the in vitro model. SPP was the most effective, and was therefore selected for further study of its hypoglycemic effect in vivo. SPP effectively improved body weight and glucose and lipid metabolism in type 2 diabetes model mice, in addition to exerting a protective effect on liver injury. SPP regulated the mRNA expression of key PI3K/Akt genes involved in the insulin signaling pathway. The hypoglycemic mechanism of SPP may reduce hepatic insulin resistance by activating the PI3K/Akt signaling pathway. Spore powder polysaccharides (SPP) extracted from Cordyceps cicadae effectively improved body weight and glucose and lipid metabolism in type 2 diabetes model mice, in addition to exerting a protective effect on liver injury. The mechanism underlying the hypoglycemic effect of SPP regulates the mRNA expression of key PI3K/Akt genes involved in the insulin signaling pathway to alleviate insulin resistance. Our results provide a theoretical basis for research into the hypoglycemic effect of Cordyceps cicadae, and lay the foundation for the development of functional products.

Positional Distribution of Fatty Acids in Processed Chinook Salmon Roe Lipids Determined by 13C Magnetic Resonance Spectroscopy (NMR)

Recently, there has been great interest in the lipidomic of marine lipids and their potential health benefits. Processing of seafood products can potentially modify the characteristics and composition of lipids. The present study investigated the effect of processing methods (salting and fermentation) on the positional distribution of fatty acids of Chinook salmon roe using 13C nuclear magnetic resonance spectroscopy (NMR). The NMR analysis provided information on the carbonyl atom, double bond/olefinic, glycerol backbone, aliphatic group, and chain ending methyl group regions. The obtained data showed that docosahexaenoic acid (DHA) is the main fatty acid esterified at the sn-2 position of the triacylglycerides (TAGs), while other fatty acids, such as eicosapentaenoic acid (EPA) and stearidonic acid (SDA), were randomly distributed or preferentially esterified at the sn-1 and sn-3 positions. Fermentation of salmon roe was found to enrich the level of DHA at the sn-2 position of the TAG. The processing of roe by both salt drying and fermentation did not appear to affect the proportion of EPA at the sn-2 position. This present study demonstrated that fish roe processing can enhance the proportion of DHA at the sn-2 position and potentially improve its bioavailability.

Synthesis, nanostructuring and in silico studies of a new imine bond containing a macroheterocycle as a promising PBP-2a non-β-lactam inhibitor.

This study is devoted to the synthesis of a 40-membered macroheterocycle with its further nanostructuring by magnetite nanoparticles. The mentioned macroheterocycle was synthesized by the [2+2] cyclocondensation of the oxygen-containing diamine with an aromatic dialdehyde in a non-catalytic medium and with no work-up procedure. The structure of the obtained macroheterocycle was studied by 1H and 13C nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Furthermore, the nanosupramolecular complex of macroheterocycles with magnetite nanoparticles was obtained and investigated by Fourier-transform infrared and ultraviolet-visible spectroscopy methods. Shifts in the infrared spectra of the nanosupramolecular complex indicate the interaction through metal-aromatic ring non-covalent bonding. The shift is also observed for the C-O-C stretching band of ether bonds. The loading rate of macroheterocycles on magnetite nanoparticles was 18.6%. The morphology of the ensemble was studied by transmission electron microscopy, which confirmed the synthesis of nanospherical particles with a diameter range of 10-20 nm. Powder X-ray diffraction analysis showed patterns of cubic Fe3O4 nanoparticles with a crystallite size equal to 9.1 nm. The macroheterocycle and its nanosupramolecular complex were tested against Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. The results have shown that the created complex has shown 64 times better activity against Staphylococcus aureus in comparison with the individual macroheterocycle and 32 times better activity in comparison with the pristine antibiotic Ampicillin as a control. In addition, computational analysis of the macroheterocycle was performed at the B3LYP/6-31G level in water. Molecular docking analyses for the macroheterocycle revealed Penicillin-binding protein PBP2a (5M18) from the transpeptidase family as a target protein in Staphylococcus aureus.

Preliminary Analysis of Unsaturated Fatty Acid Profiles of Coffea arabica L., in Samples with a Denomination of Origin and Speciality of Oaxaca, Mexico.

In February 2020, Coffea arabica L. grown on the coast and in the Southern Sierra Madre of the state of Oaxaca, Mexico obtained the denomination of origin. Which does not have data on color and chemical composition, the first associated with the degree of roasting and the second with lipids (17-18%), as the group of compounds responsible, in part, for flavor, consistency, and may contribute to health benefits. In the present work, color was determined on the CIE L*a*b* scale and the unsaturated fatty acids by Nuclear Magnetic Resonance (NMR) of 1H and 13C in samples of medium roasted specialty coffee from the "Pluma" coffee-growing region, Oaxaca, Mexico. The average value of L* luminosity in ground coffee was 42.1 ± 0.1 reported for a light roast. Unsaturated fatty acids were quantified from the lipid fraction of the gr1 ound grain by NMR 1H and 13C, obtaining on average the highest abundance of linoleic (41.7 ± 0.5 by 1 H and 41.24 ± 0.5 by 13C), followed by oleic (9.2 ± 0.2 by 1H and 7.4 ± 0.2 by 13C) and linolenic (1.5 ± 0.1 by H and 1.1 ± 0.2 by 13C). This study indicates that 1H and 13C NMR spectroscopy is a useful tool for the quantification of linolenic, linoleic, and oleic fatty acids by the method of key signal shifts of these acids found in lipid samples in roasted coffee grains.

A convenient synthesis, characterization and biological evaluation of novel schiff base heterocycles as potential antimicrobial, antitubercular agents and their structural activity relationship

A series of (E)-1-methyl-3-((substituted phenylimino)methyl)quinolin-2(1H)-one schiff bases (3a-j) bearing quinoline moiety synthesized successfully in ethanol by condensation of starting material 1-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehyde (1) with various substituted anilines (2a-j). The structure of the newly synthesized compounds was confirmed by proton (1H) and carbon (13C) nuclear magnetic resonance spectroscopy, Fourier transformation infrared (FT-IR), Mass spectroscopic study and elemental analysis. The in-vitro antimicrobial activity of the synthesized compounds was undertaken by agar well diffusion method against gram positive bacteria (Bacillus licheniformis and Bacillus cereus) gram negative bacteria (Escherichia coli and Acetobactor sp.) and antifungal activity against (Aspergillus Flavus and Pichnanomala). Further the compounds which shows good activity (3b, 3c, 3d, 3f, 3g and 3j) are screened for in-vitro antitubercular activity by Micro-plate alamar blue assay (MABA) method against mycobacterium tuberculosis H37Rv strain provided important information about activity against these strains. The structure activities of the synthesized compounds were also discussed. Compounds 3a, 3c, 3d, 3f and 3g show good argument with the different substituent attached to the phenyl ring.

One-bond 13C-13C spin-coupling constants in saccharides: a comparison of experimental and calculated values by density functional theory using solid-state 13C NMR and X-ray crystallography.

Methyl aldohexopyranosides were 13C-labeled at contiguous carbons, crystallized, and studied by single-crystal X-ray crystallography and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy to examine the degree to which density functional theory (DFT) can calculate one-bond 13C-13C spin-coupling constants (1JCC) in saccharides with sufficient accuracy to permit their use in MA'AT analysis, a newly-reported hybrid DFT/NMR method that provides probability distributions of molecular torsion angles in solution (Zhang et al., J. Phys. Chem. B, 2017, 121, 3042-3058; Meredith et al., J. Chem. Inf. Model., 2022, 62, 3135-3141). Experimental 1JCC values in crystalline samples of the doubly 13C-labeled compounds were measured by solid-state 13C NMR and compared to those calculated from five different DFT models: (1) 1JCC values calculated from single structures identical to those observed in crystalline samples by X-ray crystallography (all atom refinement); (2) 1JCC values calculated from the single structures in (1) but after Hirshfeld atom refinement (HAR); (3) 1JCC values calculated from the single structures in (1) after DFT-optimization of hydrogen atoms only; and (4 and 5) 1JCC values calculated in rotamers of torsion angle θ2 (C1-C2-O2-O2H) or ω (C4-C5-C6-O6) from which either specific or generalized parameterized equations were obtained and used to calculate 1JCC values in the specific θ2 or ω rotamers observed in crystalline samples. Good qualitative agreement was observed between calculated 1JCC values and those measured by solid-state 13C NMR regardless of the DFT model, but in no cases were calculated 1JCC values quantitative, differing (over-estimated) on average by 4-5% from experimental values. These findings, and those reported recently from solution NMR studies (Tetrault et al., J. Phys. Chem. B 2022, 126, 9506-9515), indicate that improvements in DFT calculations are needed before calculated 1JCC values can be used directly as reliable constraints in MA'AT analyses of saccharides in solution.

Antiproliferative, Anti-Inflammatory and Anti-Microbial Activities of Synthesized Benzo[f]benzo[4,5]imidazo[1,2-d][1,4]oxazepine and Benzo[f]benzo[4,5]oxazolo[3,2-d][1,4]oxazepine Derivatives

Synthesized benzoxazepine derivatives have been characterized and evaluated using 1 H, 13C nuclear magnetic resonance (NMR), DEPT 135 (distortionless enhancement by polarization transfer), and high resolution mass spectrometry (HRMS) to confirm the leading benzoxazepine chemical structures. X-ray crystal structure of compounds 10 and 13 (10,11-dimethyl-6,7-dihydrobenzo[f] benzo[4,5]imidazo[1,2-d][1,4]oxazepine and 8,9-dihydrobenzo[4,5]imidazo[1,2-d]naphtho[1,2-f] [1,4]oxazepine) were obtained after successful diffraction of the compound crystals. The anti-microbial, anti-cancer and anti-inflammatory activities of the synthesized benzoxazepine derivatives were evaluated. The effect of benzoxazepine derivatives on cancer cell proliferation and microbial growth was studied. Our results revealed limited antimicrobial activity to the synthesized benzoxazepine derivatives with significant activities against certain bacterial pathogens for two compounds. The synthesized benzoxazepine derivatives displayed cytotoxicity against selected solid tumor cell lines with varying effects on the release of human interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) pro-inflammatory cytokines depending on the cancer cell type used. The results of the study suggest that the synthesized benzoxazepine derivatives show anti-cancer and anti-inflammatory agents, though with dependence on the type of cancer cell line.

Synthesis, Cannabinoid Receptor Targeted Molecular Docking of Some New Pyrazole Derivatives as Hypolipidemic and Anti- Obesity Agents

Obesity is a serious health problem of 21st century. Around 1 billion adults are overweight and more than 300 million people are found to be obese globally. In fact 2.6 million people die per year due to obesity and thus it has now become a major reason of morbidity and mortality. In line to this few novel pyrazole derivatives (Z)-3-(4-subtituted phenyl)-2-(3, 5-dimethyl-1H-pyrazol-1-yl)-1-phenylprop-2-en-1-one (4a-f) were synthesized from 3, 5 dimethyl pyrazole by a simple inexpensive, rapid method. All compounds were authenticated using different physical and analytical techniques such as Infrared, 1H nuclear magnetic resonance, 13C nuclear magnetic resonance and mass spectrometry. Hypolipidemic activity was carried out for all the compounds using Triton WR 1339 induced hyperlipidemia model in rodents. Further, molecular docking was performed to understand the receptor-ligand interactions of synthesized compounds with cannabinoid receptor (protein data bank code: 5TGZ) using Argus lab 4.0, followed by anti-obesity studies of the selected compound (Z)-3-(4-chlorophenyl)-2-(3, 5-dimethyl-1H-pyrazol-1-yl)-1-phenylprop-2-en-1-one (4b). Amongst six compounds four compounds showed significant reduction in cholesterol levels in along with triglyceride levels in hyperlipidemic rats. Compound 4b also caused significant elevation in % high density lipoprotein levels of rats comparable to the standard Gemfibrozil. All these compounds showed good interactions with the target protein. Compound 4b (5 mg/kg and 10 mg/kg orally), caused notable reduction in body weight of high fat diet rats. Compound 4b i.e. (Z)-3-(4-chlorophenyl)-2-(3,5-dimethyl-1H-pyrazol-1- yl)-1-phenylprop-2-en-1-one has ability to reduce body weight and improve lipid profile in rats and requires further studies to establish its safety and efficacy in preclinical and clinical subjects.

Novel pirfenidone derivatives: synthesis and biological evaluation.

In order to discover novel anti-pulmonary fibrosis agents, a series of novel pirfenidone derivatives were designed and synthesized. All compounds were investigated for their anti-pulmonary activity and characterized by 13C and 1H nuclear magnetic resonance and high-resolution mass spectrometry. Preliminary studies on their biological activity showed that all target compounds showed different degrees of inhibition on pulmonary fibrosis, and most of the derivatives were significantly better than pirfenidone.

Linear Correlation between True Density and Crystallinity of Regenerated and Mercerized Celluloses.

Regenerated and mercerized celluloses are widely used in our daily life and industries. Examples include clothes, medical supplies, and separation membranes. In such applications, the true density is an important derived physical quantity for refining the structural designs of regenerated and mercerized celluloses. Here, we report the true density-crystallinity correlation of regenerated and mercerized celluloses. Seven samples were prepared through either dissolution-regeneration or mercerization, and the true density of each sample was measured by helium gas pycnometry. The crystallinity was evaluated by solid-state 13C nuclear magnetic resonance spectroscopy based on the ratio of the carbon atoms in the crystallite core to those at crystallite surfaces and in the surrounding amorphous matrix. We found that the true density of regenerated and mercerized celluloses is directly proportional to crystallinity, irrespective of the preparation process. Additionally, the molecular packing density at the crystallite surfaces was found to be similar to that in the amorphous matrix.

Molecular Model Construction and Optimization Study of Gas Coal in the Huainan Mining Area

To construct the macromolecular model of gas coal in the Huainan mining area, 13C nuclear magnetic resonance spectroscopy (13C-NMR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) tests were used to analyze the microstructure characteristics of coal including the aromatic ring type, the linkage mode, and the chemical bonding composition. The model was simulated and optimized by molecular mechanics (MM) and molecular dynamics (MD). The experimental results showed that the coal macromolecular formula in the Huainan mine was expressed as C181H150O9N3. The aromatic ring was dominated by anthracene and phenanthrene. Aliphatic carbon mainly existed in the form of methylene and methine. The oxygen atoms existed in the form of ether−oxygen bonds. The ratio of pyridine nitrogen to pyrrolic nitrogen was 2:1. The molecular simulation results showed the π−π interaction between the aromatic lamellae within the molecule. The van der Waals energy was the major factor of coal molecular structure stability and energy change. The results of the calculated 13C-NMR carbon spectrum and density simulation agreed well with the experimental results. The study provides a scientific and reasonable method for coal macromolecular model prediction and theoretical support for coal spontaneous combustion prevention technology.

Morphological, Mechanical, and Antimicrobial Properties of PBAT/Poly(methyl methacrylate-co-maleic anhydride)-SiO2 Composite Films for Food Packaging Applications.

A poly(methyl methacrylate-co-maleic anhydride) P(MMA-co-MA) copolymer was synthesized via radical polymerization. The synthesized P(MMA-co-MA) copolymer was identified by 1H- and 13C-nuclear magnetic resonance spectroscopy (1H-NMR), (13C-NMR), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The poly(butylene adipate-co-terephthalate) (PBAT)/P(MMA-co-MA)-SiO2 composites were developed using a solution-casting method. The PBAT to P(MMA-co-MA) weight ratio was kept at 70:30, while the weight percentage of SiO2 nanoparticles (NPs) was varied from 0.0 to 5.0 wt.%. SiO2 was used for PBAT/P(MMA-co-MA) to solve the compatibility between PBAT and the P(MMA-co-MA) matrix. The PBAT/P(MMA-co-MA)-SiO2 composites were characterized by studied FTIR spectroscopy, XRD, SEM, and TEM. A comparison of the composite film PBAT/P(MMA-co-MA)-SiO2 (PBMS-3) with the virgin PBAT and P(MMA-co-MA) film revealed its good tensile strength (19.81 MPa). The WVTR and OTR for the PBAT/P(MMA-co-MA)-SiO2 composites were much smaller than for PBAT/P(MMA-co-MA). The PBAT/P(MMA-co-MA)-SiO2 WVTR and OTR values of the composites were 318.9 ± 2.0 (cc m-2 per 24 h) and 26.3 ± 2.5 (g m-2 per 24 h). The hydrophobicity of the PBAT/P(MMA-co-MA) blend and PBAT/P(MMA-co-MA)-SiO2 composites was strengthened by the introduction of SiO2, as measured by the water contact angle. The PBAT/P(MMA-co-MA)-SiO2 composite films showed excellent antimicrobial activity against the food-pathogenic bacteria E. coli and S. aureus from the area of inhibition. Overall, the improved packaging characteristics, such as flexibility, tensile strength, low O2 and H2O transmission rate, and good antimicrobial activities, give the PBAT/P(MMA-co-MA)-SiO2 composite film potential for use in food packaging applications.

13C NMR study of amino acid salts in facilitated transport membranes for post-combustion carbon capture

Some of amino acid salts (AASs) have been demonstrated to be effective mobile carriers in facilitated transport membranes (FTMs) to achieve superior CO2 permeance and CO2/N2 selectivity for CO2 capture from flue gas. Understandings of how the structures of different AASs affect the chemistry of the amine–CO2 reaction are essential for the future development of more efficient AAS mobile carriers. In this study, the reaction chemistry of selected AASs with CO2 was investigated by 13C nuclear magnetic resonance (NMR) spectroscopy. The CO2 loading and the distribution of major reaction products, including carbamate and bicarbonate products of each studied AAS were quantitatively analyzed. The positive correlation between the CO2 loading of AAS (mol CO2/g AAS) and the CO2 permeance of FTMs suggested that AAS with a higher CO2 loading may improve the performance of FTMs. Our results also showed that increasing the steric hindrance of AAS could be a practical way to promote the bicarbonate reaction pathway and thus potentially increase the CO2 loading (mol CO2/mol AAS). Moreover, 2-(1-piperazinyl)ethylamine (PZEA) was found to be a more effective multi-amine than piperazine (PZ) for synthesizing AASs due to the presence of more effective nitrogen sites per molecule. The superior CO2 permeance of the PZEA-Sar membrane is also attributed to its more uniform membrane formation. The knowledge gained from this study will inform the rational design of more effective AAS carriers for CO2 capture.