A systematic study of solvent effect on the crystal habit of dirithromycin solvates by computer simulation

The crystal habits of five dirithromycin solvates were employed to unravel the solvent effect by using the modified attachment energy (AE) model. Solvents with different polarity and hydrogen bond donor/acceptor ability (acetone, 1-propanol, acetonitrile, water and cyclohexane) were studied. The good consistency between experimental results and predictions confirmed the applicability of modified AE model. Simulation results showed that all solvates underwent a change in morphological importance (MI) of crystal faces except for the cyclohexane trisolvate. A detailed analysis of the results indicated that the polar solvent had a stronger interaction with crystal face than the non-polar solvent due to the formation of hydrogen bond. Furthermore, crystals with similar structure in different solvents exhibited different aspect ratios. The computer-aided study approach in this work could be helpful to control the morphology of crystal by tailor-made solvents or additives.     

Investigation of CO2 solubility in monoethanolamine hydrochloride based deep eutectic solvents and physical properties measurements

Deep eutectic solvents (DESs) have drawn a growing research interest for applications in a wide range of scientific and industrial arenas. However, a limited effort has been reported in the area of gas separation processes and particularly the carbon dioxide capture. This study introduces a novel set of DESs that were prepared by complexing ethylenediamine (EDA), monoethanolamine (MEA), tetraethylenepentamine (TEPA), triethylenetetramine (TETA) and diethylenetriamine (DETA) as hydrogen bond donors to monoethanolamide hydrochloride (EAHC) salt as a hydrogen bond acceptor. The absorption capacity of CO₂ was evaluated by exploiting a method based on measuring the pressure drop during the absorption process. The solubility of different DESs was studied at a temperature of 313.15 K and initial pressure of 0.8 MPa. The DES systems 1EAHC:9DETA, 1EAHC:9TETA and 1EAHC:9TEPA achieved the highest CO₂ solubility of 0.6611, 0.6572 and 0.7017 mol CO₂·(mole DES)⁻¹ respectively. The results showed that CO₂ solubility in the DESs increased with increasing the molar ratio of hydrogen bond donor. In addition, the CO₂ solubility increased as the number of amine groups in the solvent increases, therefore, increasing the alkyl chain length in the DESs, resulted in increasing the CO₂ solubility. FTIR analysis confirms the DES synthesis since no new functional group was identified. The FTIR spectra also revealed the carbamate formation in DES-CO₂ mixtures. In addition, the densities and viscosities of the synthesized DESs were also measured. The CO₂ initial investigation of reported DESs shows that these can be potential alternative for conventional solvents in CO₂ capture processes.     

On the equilibrium and dynamic behavior of alcohol vapors in activated carbon

As alcohol molecules such as methanol and ethanol have both polar and non-polar groups, their adsorption behavior is governed by the contributions of dispersion interaction (alkyl group) and hydrogen bonding (OH group). In this paper, the adsorption behavior of alcohol molecules and its effect on transport processes are elucidated. From the total permeability (B_T) of alcohol molecules in activated carbon, an adsorption mechanism is proposed, describing well the experimental data, by taking combination effects of clustering, entering micropores, layering and pore filling processes. Unlike the case of non-polar compounds, it was found that at low pressures there are two rises in the B_T of alcohol molecules in activated carbon. The first rise is due to the major contribution of surface diffusion to the transport (which is the case of non-polar molecules) and the second one may be associated with cluster formation at the edge of micropores and entering micropores when the clusters are sufficiently large enough to induce a dispersive energy. In addition the clusters formed may enhance surface diffusion at low pressures and hinder gas phase diffusion and flow in meso/macropores.     

Electrokinetic and solvatochromic studies of functionalized silica particles

Zeta potential plots, Kamlet-Taft's α (hydrogen bond-donating, HBD), β (hydrogen bond-accepting, HBA), and π* (dipolarity/polarizability) parameters as well as Gutmann's DN (donor numbers) are presented for 12 differently functionalized (i.e. alkyl, cyanoalkyl, aminoalkyl, and imidazolidine) silica particles. The pH-dependent zeta potential plots were measured in aqueous solution, whereas the solvatochromic studies were performed in 1,2-dichloroethane and cyclohexane as solvents using a special UV/visible spectroscopic technique. For the determination of the solvatochromic polarity parameters, a set of carefully characterized polarity indicators was employed: Cu(tmen)(acac)⁺B(C₆H₅)₄ ^- for β and DN; dicyano-bis(1,10-phenanthroline)iron(II) for α; 4,4′-bis(N,N-dimethylamino)benzophenone for π*; and an aminobenzofuranone derivative {3-(4-amino-3-methylphenyl)-7-phenyl-benzo[1,2b : 4,5b′]difuran-2,6-dione} (ABF) for α, β, and π*. The calculation of the polarity parameters was carried out via linear solvation energy (LSE) correlation equations using the Kamlet-Taft solvent parameters as a reference system. A linear correlation between the electrokinetically determined value of the isoelectric point and the β parameter of the functionalized silicas is demonstrated.     

Obtaining protein solvent accessible surface area when structural data is unavailable using osmotic pressure

Here, we provide an algorithm that predicts solvent accessible surface area (SASA) using concentrated solution osmotic pressure data. Sheep hemoglobin monomer and β‐lactoglobulin are used for verification. Additionally, SASA for structurally unknown calf lens α‐crystallin aggregate is predicted. Using osmotic pressure data, the predicted SASA value for sheep hemoglobin, 22,398 ± 1,244 Ų, was in excellent agreement with computational model predictions (24,304 Ų‐26,100 Ų). Similarly, predicted SASA values for bovine β‐lactoglobulin in pH solutions of pH 5.1, 6.0, and 8.0, were 5,765 ± 1,031 Ų, 6,656 ± 1,082 Ų, and 9,141 ± 1,060 Ų, respectively, were in good agreement with the computationally determined SASA value (7,500 Ų–8,628 Ų). Predicted SASA for the aggregate of calf lens α‐crystallin (800 kDa) was found to be 417,691 ± 16,790 Ų. These results illustrate that this novel method can provide an important experimental alternative in estimating SASA for proteins and, possibly, their complexes in solution. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Effect of reactive diluent on gas separation behavior of photocurable acrylated polyurethane composite membranes

In this study, the effects of the type and content of reactive diluents on the permeation/separation of carbon dioxide/nitrogen (CO₂/N₂) through acrylate-terminated polyurethane (APU)-acrylate/acrylic diluent (APUA) composite membranes was investigated. A series of APUs based on poly(ethylene glycol) (PEG)-1000 g mol⁻¹, toluene diisocyanate, and 2-hydroxyethyl methacrylate was synthesized and then diluted with several reactive diluents. The results obtained from differential scanning calorimetry (DSC) and Fourier transform infrared analyses showed that the microphase interference of hard and soft segments increased with increasing reactive diluent content. Furthermore, with increasing alkene double bond of reactive diluents, the degree of phase separation increased, which might be due to the higher gel content of APUAs. APUAs were used as top selective layer on PS/PSF as the support layer to obtain composite membrane. Field emission scanning electron microscopy micrographs revealed that APUAs penetrated into the support layer, leading to strong interfacial adhesion between APUA and support layers. The gas permeation experiments indicated that the gas permeability decreased, while the CO₂/N₂ selectivity increased with increasing reactive diluent content due to the enhancement of crosslinking density of APUAs. Moreover, the reactive diluent with high polarity, for example, acrylonitrile monomer, exhibited higher CO₂/N₂ selectivity due to the improvement in solubility of CO₂ in APUA, while the permeability was retained compared with other reactive diluents. The thickness of APUA selective layer exhibited expectedly opposite effect on permeability and selectivity; however, the increment in selectivity is higher than the reduction in permeability when the thickness decreased from 50 to 10 μm. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48293.     

Cohesive energy densities of poly(di-n-alkyl itaconates)

The solubility parameters of the first ten members of the homologous series of poly(di-n-alkyl itaconates) were determined from limiting viscosity numbers in various organic solvents, differing in structure, polarity and hydrogen bonding capacity. Numerical values from 9.58 to 8.10 (cal/cm³)^1/2 were obtained independently from measurements in hydrocarbon and oxygen containing solvents, close to solubility parameters calculated from polymer densities and molar attraction constants. The values obtained reflects the increasing paraffinic character within the series and can be correlated to solubility parameters published in the literature for structurally similar poly(alkyl acrylates) and poly(alkyl methacrylates).     

Statistical thermodynamics of group interaction in n-alkane-n-alkanol and n-alkanol-n-alkanol solutions

The statistical thermodynamics previously developed for pure liquids of non-polar and polar chain molecules is extended to their mixtures. An orientation factor is introduced into the quasi-chemical relation of the hydrogen bond to reduce the calculated preferential bonding. Excess properties are calculated for n-alkane-n-alkanol-1 and n-alkanol-1-n-alkanol-1 solutions. The heat of mixing and excess free energy calculated with the group properties reported previously are in good agreement with data for solutions in which the alkanol is higher than ethanol.     

Crosslinking mechanism of supramolecular elastomers based on linear bifunctional polydimethylsiloxane oligomers

Supramolecular elastomers (SESis) were synthesized via a simplified synthesis route on the basis of a linear bifunctional polydimethylsiloxane. Compared with previous synthesis methods, the structure of the product was much clearer. The ¹H‐NMR titration results show that the hydrogen‐bond associations in SESis were relatively weak. During ¹H‐NMR reaction monitoring, the viscosity analysis of SESis and the model reactions demonstrated a previously neglected covalent crosslinking reaction not only during the reaction process but also during the postprocess; this led to a hybrid network, that is, covalent crosslinking and hydrogen association, in SESis. This finding explained the poor solubility of the SESis, and it provides us with an important way to controllably synthesize this material and adjust its properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43385.     

Hydrogen-Bond Dynamics and Solvation of Electronically Excited States as Determined by Femtosecond Vibrational Spectroscopy

The ultrafast dynamics of site-specific hydrogen bonds between an organic chromophore serving as hydrogen acceptor and a hydrogen-donating species in solution is studied by femtosecond vibrational spectroscopy. This new method gives specific insight into microscopic structural changes of hydrogen bonds initiated by electronic excitation of the chromophore. We study H-bonded complexes of coumarin 102 with the solvent CHCl₃, and with phenol. Upon electronic excitation, the intermolecular hydrogen bond between proton donor and acceptor is cleaved within 200 fs, followed by a slower reorientation dynamics of the donor molecules extending into the picosecond regime. For CHCl₃, this slower rearrangement is interpreted in terms of polar solvation. In complexes consisting of a coumarin molecule and two phenol moieties, the slower dynamics is related to geometry changes of the phenol–phenol hydrogen bond. The consequences of those results for a microscopic picture of polar solvation are discussed.     

红外光谱测量法研究超临界CO2中夹带剂与溶质的相互作用

利用红外光谱技术研究了在超临界CO₂中加入不同夹带剂时，水杨酸中基团的伸缩振动频率的位移及夹带剂与溶质的相互作用。以乙醇为夹带剂时，水杨酸中C=O基团、O—H基团的伸缩振动频率均向低频方向移动;以丙酮为夹带剂时，水杨酸中C=O基团伸缩振动频率向高频方向移动。研究结果表明：当以乙醇为夹带剂时，水杨酸的溶解度远大于以丙酮为夹带剂时的结果，夹带剂对溶质增溶的作用能力，形成氢键的作用远大于溶剂极性的作用。     

Examination of the surface properties of kaolinites by inverse gas chromatography: Acid-base properties

The specific component of the free energy of adsorption,-ΔG _A ^SP , of untreated kaolinite and kaolinites surface-treated with isopropyl triisostearoyl titanate (ITT) and isopropyl tri(dioctylpyrophosphato) titanate (ITDT) was estimated, using the adsorption of several polar and non-polar probes on these surfaces at various measuring temperatures, by the inverse gas chromatography (IGC) method. The acid-base properties of the untreated kaolinite and surface-treated kaolinites were quantified by K _A and K _D parameters, reflecting the ability of the surface to act as an electron acceptor and donor, respectively. In the result, all kaolinite surfaces were amphoteric and were able to function as both an electron acceptor and an electron donor.     

Gas diffusion electrodes improve hydrogen gas mass transfer for a hydrogen oxidizing bioanode

Background

Bioelectrochemical systems (BESs) are capable of recovery of metals at a cathode through oxidation of organic substrate at an anode. Recently, also hydrogen gas was used as an electron donor for recovery of copper in BESs. Oxidation of hydrogen gas produced a current density of 0.8 A m^‐2 and combined with Cu²⁺ reduction at the cathode, produced 0.25 W m^‐2. The main factor limiting current production was the mass transfer of hydrogen to the biofilm due to the low solubility of hydrogen in the anolyte. Here, the mass transfer of hydrogen gas to the bioanode was improved by use of a gas diffusion electrode (GDE).

Results

With the GDE, hydrogen was oxidized to produce a current density of 2.9 A m^‐2 at an anode potential of –0.2 V. Addition of bicarbonate to the influent led to production of acetate, in addition to current. At a bicarbonate concentration of 50 mmol L^‐1, current density increased to 10.7 A m^‐2 at an anode potential of –0.2 V. This increase in current density could be due to oxidation of formed acetate in addition to oxidation of hydrogen, or enhanced growth of hydrogen oxidizing bacteria due to the availability of acetate as carbon source. The effect of mass transfer was further assessed through enhanced mixing and in combination with the addition of bicarbonate (50 mmol L^‐1) current density increased further to 17.1 A m^‐2.

Conclusion

Hydrogen gas may offer opportunities as electron donor for bioanodes, with acetate as potential intermediate, at locations where excess hydrogen and no organics are available. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Hansen Solubility Parameters as a Tool in the Quest for New Edible Oleogels

By identifying the Hansen space of nonfood‐grade gelators, which are capable of gelling oil, insights into the molecular characteristics required for gelation of edible oil become apparent. In examining the 34 reported oleogelators, molecules that gel oil tend to have a dispersive Hansen solubility parameter (HSP) between 16.0 < δ_d > 17.5 MPa^1/2, a polar HSP between 7.0 < δ_p > 11.0 MPa^1/2, and a hydrogen‐bonding HSP between 7.0 < δ_h > 9.0 MPa^1/2. Although this does not define the complete Hansen space of these gelators, it provides insight into what types of molecules may be capable of forming oleogels in vegetable oils to allow new discovery without relying solely on serendipity.     

Gas transport in poly(alkoxyphosphazenes)

The permeability of four structurally related poly(alkoxyphosphazenes), three isomers of poly(dibutoxyphosphazenes) (PBuP), and poly(di-neopentyloxyphosphazene) (Pneo-PeP), to 13 gases has been determined by the time-lag method. Systematic variations in chemical structure have shown a large effect of side chains on permeabilities and permselectivities. The permeability of poly(di-n-butoxyphosphazene) (Pn-BuP) is of the order of 10^?8 cm³ (STP) cm/(cm² s cmHg) for many gases, and the value for a large gas is higher than that for a smaller one. For small gases such as He and H₂, poly(di-sec-butoxyphosphazene) (Ps-BuP) is as permeable as Pn-BuP, but its diffusivities for larger gases such as Xe and C₃H₈ are about one order lower than those of Pn-BuP. While the permselectivity of Pn-BuP is determined by the solubility, that of Ps-BuP depends on both the diffusivity and solubility factors. The property of poly(diisobutoxyphosphazene) (Pi-BuP) is intermediate between them. These polymers are constitutionally identical, and the only difference is the arrangements of carbons in the side groups. As the side chains become bulky, the permeability decreases, whereas the permselectivity increases. Further decreases of diffusivity and then permeability are observed for Pneo-PeP, whose side groups have one more methyl group than does Pi-BuP. But the solubility data are not much different from other three polymers and the diffusivity factor becomes more significant in permselectivity. The diffusivity depends on the polymer structure much more than does the solubility. The relationships between chemical structure and gas diffusivity and solubility are discussed.     

Theoretical estimation of the effect of solvent on unperturbed dimensions: 1. Isotactic poly(vinyl alcohol)

The effect of the quality of solvent on the unperturbed chain dimensions $\text{r}{}_0{}^2$ of perfectly isotactic poly(vinyl alcohol) (iso-PVA) was studied by means of some model calculations according to the matrix method of Flory et al. These investigations were based on the assumption that the quality of solvent affected mainly the energy of the intramolecular hydrogen bond, while the magnitude of the interactions between other groups, hardly varied with the change of solvent. The individual conformation energies in a chain of iso-PVA were estimated from the analysis of structurally similar polymers, as well as the results obtained with 2,4-pentanediol. It was found that the characteristic ratio $\text{C =}\text{r}{}_0{}^2\text{nl}{}^2$ increased in non-polar solvents, with energy of the intramolecular hydrogen bond stabilizing the stretched zig-zag conformation of chain. Conversely, the characteristic ratio, monotonously decreased with increasing polarity of solvent to the value of about 6, typical of a flexible random coil. The existence of an analogous relationship, valid for other polymers, able to form an intramolecular hydrogen bond in the chain, was also discussed.     

The solubility of hydrogen in aliphatic amines

The solubility of hydrogen in ammonia, monomethylamine, monoethylamine and n-propylamine was determined at temperatures from ?70°C to 25°C and in 1,2-propanediamine and 1,2-ethanediamine over the temperature ranges ?25°C to 11°C and 25°C to 34°C respectively. Measurements were made at total pressures up to 300 psig. The solubility data were correlated in terms of Henry's law and the solubilities are in the range 1 × 10^?5 to 3 × 10^?4 mole fraction at a hydrogen partial pressure of 1 atmosphere. The measured solubility data were used to extend a correlation proposed by Yen and McKetta. This revised correlation may be used to estimate the solubility of hydrogen in polar, associated amines.     

Effects of polarity and pH on the solubility of acid-treated carbon nanotubes in different media

The aggregation of acid-treated carbon nanotubes (CNTs) as a solid and their solubility in solvents of different polarity and in water of different pH were investigated as a function of acid treatment conditions. The CNTs were found to form solid hydrogen-bonded aggregates, with a higher content of COOH groups resulting in a denser aggregate. The untreated CNTs were non-polar in nature and could dissolve, or be easily dispersed, in non-polar or low polar solvents such as acetone and alcohols (methanol and ethanol), but precipitated from deionized water, a highly polar solvent. In contrast, the acid-treated CNTs dissolved or were well dispersed in the deionized water, but not in acetone or alcohols. The treated CNTs were insoluble in an aqueous solution of pH 0, but soluble in those of pH 4 and higher with their solubility monotonically increasing with pH up to pH 10. The considerable ionic bond strength between carboxylate anions and sodium cations could be a reason for a decrease of their solubility in an aqueous solution of pH 12.     

H2S absorption with deep eutectic solvents: Low partial pressure capture and thermodynamic analysis

In the present work, a series of deep eutectic solvents (DESs) based on organic amine as hydrogen bond acceptors (HBAs), and ethylene glycol (EG) as hydrogen bond donor (HBD) were prepared for the H₂S absorption. Thermal decomposition temperature, HBA mass ratios, alkalinity and structure effect on absorption behavior were systematically investigated. The reaction mechanism was demonstrated by FT-IR and ¹H NMR spectroscopy. The reaction equilibrium constants, Henry constant, enthalpy and entropy change were calculated based on the thermodynamic model to reveal the interactions between DESs and H₂S. It was found that H₂S absorption capacities of the most of DESs with HBA/HBD mass ratio of 1:4 was close to 1 mol/mol at 303.15 K and 0.2 bar. The absorption capacity of DESs depends on the alkalinity and structure of HBAs; Additionally, a good linear correlation between the alkalinity of HBA and the absorption equilibrium constant (lnK) of DESs to H₂S was found.     

Swelling characteristics of NR/PU block copolymers and the effect of NCO/OH ratio on swelling behaviour

A series of (NR/PU) block copolymers (BCs) was prepared from toluene diisocyanate (TDI), 1,3-butane diol (1,3-BDO), and hydroxyl-terminated liquid natural rubber (HTNR), by solution polymerisation. The swelling characteristics of the BCs were investigated. Diffusion profile in various solvents and the sorption kinetics were studied. Arrhenius and thermodynamic parameters were evaluated from the diffusion data. Finally, the influence of NCO/OH ratio on the swelling behaviour was also studied. The equilibrium sorption value (Q_∞) decreased with increasing NCO/OH ratio for all the BCs. The samples have higher uptake of solvents with solubility parameter within a small range centred about 9 (cal/cm³)^1/2. Highly polar and non-polar solvents show minimum uptake. It was observed that polarity factor predominates in the solvent transport through the present block copolymer systems. The sorption behavior is also found to vary with the NCO/OH ratio employed in the preparation of polyurethane (PU) oligomers.