Papers by Keyword: Hydrogen Bond

Abstract: The self-assembly system driven by hydrogen bonding has been widely used in various fields. Two hydrogen-bonded cyclophosphazene derivatives with amino groups (AGHP) and carbonyl groups (CGHP) were synthesized by introducing hydrophobic groups and amino groups and hydrophilic groups and carbonyl groups into cyclophosphazene respectively through nucleophilic substitution. After they were dissolved in oil water two phases, stable emulsion, and self-loading membrane structures were obtained through self-loading behavior. The results indicate that strong hydrogen bonding can be formed between these two cyclic phosphazene derivatives with amino and carbonyl groups. This hydrogen bonding can significantly reduce the interfacial tension between water/oil phases (from around 33 mN/m to below 7 mN/m) and improve the interfacial coverage (which can reach over 80%). Meanwhile, under the hydrogen bonding between amino and carbonyl groups, an amphiphilic self-assembled film was obtained at the water oil interface. Through contact angle testing, it was found that the hydrophilic side of this self-assembled film had a contact angle of 77.5° and the hydrophobic side had a contact angle of 124.8°.

Abstract: In this paper, chemically modified cellulose was used instead of cellulose as it offers higher adsorption capacities, great chemical strength and good resistance to heat. As part of Phyto-Adsorption Remediation Method, citric acid modified cellulose (CAMC) was used to treat ferric ion. However, there is a large possibility that CAMC molecule might interact with water molecule that contain hydrogen bond and hence pose as a competitor to ferric acid and reduces the efficiency of CAMC in ferric ion removal. Thus, the aim of this work is to identify the most stable hydrogen bond between CAMC and water, by using a computational technique. The interaction between the water molecules and CAMC was observed by varying the volume of water molecule with modified cellulose by an expansion in amorphous region. The simulation result shows that for water loading less than 20 molecules, the interaction between water molecules and CAMC is higher at temperature 311K, whilst for water loading higher than 20 molecules, the interaction weakens at higher temperature. This work proves that water molecules have the tendency to bind to carboxyl group of glucose, to oxygen of ester and to oxygen of anhydride acid of the CAMC molecule, which might pose a competition for ferric acid removal. The calculation of coordination number has shown that the number of atoms present in the first hydration shell (of radius < 2.5Å) is more as the temperature increases from 298K to 311K, which indicates that the adsorption is better at higher temperature. For hydration shell at radius >2.5Å, cell temperature is not significant to the number of atoms present.

Abstract: This work was try to study the number and types of hydrogen bonds (H-bonds) formed in hindered phenol AO-70/nitrile butadiene rubber (NBR) composites and their contributions to the damping properties by molecular dynamic (MD) simulation and experimental methods. MD simulation results showed that there were four types of H-bonds, namely, type A (AO-70) –OH...NC– (NBR) H-bonds in AO-70/NBR composites, type B (AO-70) –OH...O=C– (AO-70) H-bonds, type C (AO-70) –OH...OH–(AO-70) and D (AO-70) –OH...O–C– (AO-70) H-bonds, what's more, type A and type B H-Bonds formed more easily than others. Fourier transform infrared spectroscopy (FTIR) confirmed the existence of H-bonds. Meanwhile, the AO-70/NBR composites with AO-70 content of 109 phr had the largest number of H-bonds, smallest fractional free volume (FFV) and resulting in the optimistic damping performance of the composites.

Abstract: Conventional oil based drilling fluids or muds (OBMs) using organophilic clay as viscosifier and rheological control agent cannot carry drill cuttings and suspend weighting materials effectively in oil well drilling process. It also causes excessive viscosity of drilling fluids, which lowers the rate of penetration. For the sake of solving these problems, in this study, hydrogen bonds-enhanced organoclay-free oil based drilling fluid was proposed. Firstly key additives (emulsifier, filter reducer) for OBMs with highly electronegative groups that might form hydrogen bonds were synthesized. In addition, a hydrogen bonding linker was synthesized and used to connect other additives to form a hydrogen bonding network in OBMs. The properties of drilling fluids were characterized by rheological measurements, static filtration experiments and plugging experiments. Experimental results show that, compared with the conventional OBM, the hydrogen bonds-enhanced organoclay-free OBMs substantially increased yield point (YP) and gel strengths, reduced filtration loss and exhibited a better plugging ability on high-permeability sand cores. Besides, a higher stability was also observed.

Abstract: The effect of milling on structure of kaolinite-urea intercalates were studied. Untreated and treated kaolinite samples were examined by Field scanning electron microscopy (FESEM), X-ray powder diffraction (XRPD) and Fourier transform infrared (FT-IR) spectroscopy. The basal spacing of kaolinite measured by X-ray powder diffraction (XRPD) increased from 1.02 to 3.62 nm after intercalation by urea. Significantly, nature of intercalation was reached through formation of hydrogen bonds between urea and both Si-O and AlOH groups of the interlayer surface of kaolinite.

Abstract: Crystal morphology remains an important aspect in pharmaceutical industries and thus lengthy experimentally determined morphology becomes a routine. This leads to advancement of molecular modeling to assist in crystal morphology determination. Morphology of racemic ibuprofen can be grown in PEG 300 solvent and simulated via molecular modeling, the computational technique. The resulting morphology dictates its feasibility and prepares for further necessary control to produce desired morphology. Tuning up the morphology can be done by rationalizing out via molecular modeling the effect of the solvent and crystallization method. Solvent effect persists to influence crystal morphology mainly via interaction of hydrogen bond specific at different facets. However, the influence of solvent-surface interaction in enhancing or inhibiting crystal growth is still not completely resolved. To date, racemic ibuprofen grown in PEG 300 solvent is the first ever reported. The objective of this study is to compare experimental and predicted morphology of racemic ibuprofen using selected potential functions and charge set in vacuum condition. Racemic ibuprofen crystal morphology was grown in PEG 300 solvent via cooling at ambient temperature and predicted via attachment energy (AE) method using molecular modeling. It was found that the experimental morphology is tabular hexagonal while the predicted one is tabular octagonal. The facets were cleaved and its surface chemistry was explained. The predicted lattice energy with lowest percentage error of 0.02% is dominated by van der Waals force rather than electrostatic force.

Abstract: Modified aramid (PBIA) containing benzimidazole units in the main chain were synthesized and the corresponding PBIA fibers were prepared by wet spinning and then annealed at different temperatures. The mechanical properties and the structure of copolyamide PBIA fibers were investigated for different annealing temperatures. The results of thermogravimetric analysis showed that the decomplexation reaction between HCl and benzimidazole occurred during the annealing process and HCl was completely removed at 320°C. The decomplexation of HCl also leads to the formation of hydrogen bonds between benzimidazole fragments, resulting in the rearrangement of the molecular chain and a more ordered macromolecular structure. The mechanical properties, chain orientation could be significantly improved when the samples were annealed in the temperature range from 280 to 320 °C. In addition, the analysis of self-elongation during the annealing process further indicates that the macromolecular chains were more ordered after the decomplexation of HCl. In addition, the PBIA fibers firstly annealed at 300°C which the decomplexation reaction between HCl and benzimidazole occurred, and then annealed at 400°C, resulting the higher PBIA fibers are obtained.

Abstract: The reaction of copper 2,2-dichloroacetic acid, heterocyclic diimine (bipy) ligands under mildconditions affords one novel supramolecular complexes, [Cu (bipy)₂[[H₂₂ (bipy=2,2-bipyridine X=dichloroacetic acid). The compounds were constituted through hydrogen bonding and ππ interactions between the heterocyclic rings.

Abstract: Based on the theory of coordinate inhibition three nitrogen-containing active structures of different aromatic in coal were established. Using quantum chemistry calculation method, the effect of hydrogen bonding on the formation of complexes that formed by three nitrogen-containing active structures of different aromatic and inhibitor were calculated in B3LYP/6-311G* levels. The results show that hydrogen bond can make H₂O participation in forming complexes which formed by three nitrogen-containing active structures of different aromatic and metal ions. Hydrogen bonds play a molecular recognition and guiding role in the process of H₂O involved in the formation of complexes. After H₂O participating ligand through hydrogen bonds, the complexes formed Ca-O-H-O four-membered ring structure in the geometrical structures. It Shows that its stability are improved and not easy to contacts with O or reacting. It making coal spontaneous combustion can be well inhibition. After H₂O participating ligand, aromatic change had little effect in stability of the complexes. It shows that different ranks of coal can get better inhibition effect after H₂O participating ligand.

Abstract: The Eu complex C₄H₁₀EuO₁₀ has been synthesized from a hydrothermal reaction and the crystal structure has been determined by means of single-crystal X-ray diffraction. The Eu atom is coordinated by nine O atoms. The molecular structure stabilized by the O-H…O hydrogen-bonding interactions.