Polar-polar Interaction Research Articles

A robust sulfur host with dual lithium polysulfide immobilization mechanism for long cycle life and high capacity Li-S batteries

Beyond the physical lithium polysulfide (Li2Sx) entrapment of various 3D porous sulfur hosts, the importance of chemical interactions between sulfur host and Li2Sx on performance of Li-S batteries has recently been highlighted. However, most of these studies focus mainly on one type of chemical interaction and effective suppression of Li2Sx migration is still lacking. Here, we report a uniquely designed sulfur host that can immobilize Li2Sx through a dual chemisorption mechanism. The new sulfur host is consisted of an MXene matrix and polydopamine (PDA) overcoat, where Mxene forms a strong Ti–S bonding by the Lewis acid-base mechanism while PDA withholds Li2Sx through the polar-polar interaction. Benefited from the double chemisorption, the new cathode with a high sulfur loading of 5 mg cm−2 has been demonstrated with an initial capacity of 1001 mA h g−1 at a capacity retention of 65% over 1000 cycles at 0.2 C. Overall, this study not only presents a unique chemical mechanism to entrap Li2Sx, but also provides a new way to rationally design a practical sulfur cathode for high-performance Li-S batteries.

Aluminium trihydroxide: Novel reinforcing filler in Polychloroprene rubber

Aluminium trihydroxide (ATH) nano particles with rod like morphology were incorporated in Polychloroprene (CR) rubber by melt mixing method, to prepare nanocomposites with enhanced mechanical, thermal, sorption and dielectric properties. The effect of ATH loading on various properties of the nanocomposites was studied and the results were correlated with the microstructure of the composites using TEM, SEM and XRD analysis. Tensile strength and modulus were found to be improved by the addition of ATH, the enhancement in former being 27% at 10 phr of ATH loading. The incorporation of ATH improved the thermal stability with an increment of up to 31 °C in the maximum degradation temperature. Differential scanning calorimetry studies show marginal increase (3 °C) in glass transition temperature (Tg) at 10 phr of ATH. Dynamic mechanical studies indicate agglomeration of ATH particles at higher loadings. The experimentally obtained storage modulus values have been compared with theoretical prediction, using different composite reinforcement models. The transport properties and dielectric permittivity of the composites registers enhancement with the addition of ATH. The improvement in properties by the addition of ATH is attributed to the polar-polar interaction between the matrix and filler particles. The present study confirms that ATH can be an effective reinforcing filler for CR matrix.

Preparation and Characterization of North Sumatera Natural Zeolite Polyurethane Nanocomposite Foams for Light-weight Engineering Materials

Normally, the mechanical properties of commercial polyurethane foams are relatively low when used for light-weight engineering materials such as for low-energy automotive construction. In the present work, light-weight polyurethane nanocomposite foams were prepared using natural zeolites of North Sumatera as filler. The zeolite fillers were prepared using ball milling technique and their particle size distributions were characterized using particle size analyzer. The nanocomposite foams, prepared using in-situ reaction of polypropylene glycol and toluene diisocyanate were then characterized for Tensile, morphology properties and XRF analysis. Data in this paper only tensile, morphology properties and XRF analysis. The compositions of nanofiller in polyurethane matrices were varied from 5% - 25wt%. It was found that tensile strength and Modulus of elasticity (MOE) of polyurethane nanocomposites containing 20% of zeolite were 2,9MPa and 11.1MPa respectively, which showed higher values when compared to those of unfilled polyurethane. The presence of nanozeolite filler has funtioned as reinforcement in nanocomposites through polar-polar interaction between the filler surfaces with the matrix. Furthermore, the SEM result did not show any agglomeritation of the nanozeolites fillers in the polyurethane matrix, which may be due to better interaction between the matrix and the filler.

Preparation and Characterization of Microwave-absorption of Sarulla North Sumatra Zeolite and Ferric Oxide-filled Polyurethane Nanocomposites

Microwave-absorptive polymeric composite materials are becoming important to protect interference of any communication systems due to the increase in the use of microwave-inducing devices. In this work, the microwave-absorptive polyurethane composites are prepared using natural zeolites of Sarulla North Sumatra and commercial ferric-oxide as fillers. Weight ratio of the natural zeolite to ferric oxide were varied (18:2; 16:4; 14:6; 12:8 and 10:10) by weight. The fillers are prepared using ball milling technique and characterized using Particle Size Analyzer for particle size distribution. The nanocomposites, prepared using in-situ reaction of polyethylene glycol and toluene diisocyanate, is characterized for physical and mechanical properties using tensile strength, thermal properties with TGA techniques, as well as morphological and chemical properties using scanning electron microscopy. Composition and loading of the nanofillers against polyurethane matrices is 20% by weight. Microwave-absorption properties of the nanocomposites is characterized using 8-12GHz frequency. Tensile strengths of the natural zeolite-ferric oxides polyurethane nanocomposites shows higher values when matrices filled with lower ferric-oxide, which could be due to the nanozeolites have functioned as reinforcement for the polyurethane matrix through polar-polar interaction between the filler surfaces with the matrices. The microwave absorption properties, which investigated by Vector Network Analyzer, of the nanocomposites filled in polyurethane with the ratio of nanozeolite to ferric oxide filler of 12:8 shows reflection loss of – 13.2dB. This condition was observed at 11.1GHz.

Apparent shear sensitivity of molecular rotors in various solvents.

Fluorescent environment-sensitive dyes often change their spectral properties concomitantly with multiple solvent properties, such as polarity, protonation, hydrogen bond formation, or viscosity. Careful consideration of the response is needed when a fluorescent dye is used to report a single property. Recently, we observed an increase of emission intensity of viscosity-sensitive molecular rotors in fluids subject to flow and speculated that either polar-polar interaction or hydrogen bond formation play a role in the apparent flow sensitivity. In this study, we show experimental evidence that photoisomerization to an isomer with a lower quantum yield, first proposed by Rumble et al. (J Phys Chem A 116(44):10786-10792, 2012), plays a key role in the observed phenomenon. We subjected four molecular rotors with different electron acceptor motifs to fluid flow in solvents of different polarity and ability to form hydrogen bonds. We also measured the isomerization dynamics in a custom fluorophotometer with extremely low light exposure. Our results indicate that the photoisomerization rate depends both on the solvent and on the electron acceptor group, as does the recovery of the original isomer in the dark. In most solvents, recovery of the dark isomer is much more rapid than originally reported, and a state of quasi-equilibrium between both isomers is possible. Moreover, the sensitivity (i.e., relative intensity increase at the same flow rate) is also solvent-dependent. The intensity increase can be detected at very low velocities (as low as 0.06 mm/s). Characteristic for fluorescent dyes is the high spatial resolution, and no flow measurement device with comparable sensitivity and spatial resolution exists, although the nature of the solvent needs to be taken into account for quantitative flow measurement.

Interface control of a morphotropic phase boundary in epitaxial samarium modified bismuth ferrite superlattices

Interfacial control of a polar-(rhombohedral) to-non-polar (orthorhombic) phase transition in (001)-oriented epitaxial $\mathrm{BiFe}{\mathrm{O}}_{3}\text{/}(\mathrm{B}{\mathrm{i}}_{1\ensuremath{-}x}\mathrm{S}{\mathrm{m}}_{x})\mathrm{Fe}{\mathrm{O}}_{3}$ superlattices is presented. We demonstrate controlling the composition at which a polar phase transformation takes place by tuning the strength of the interlayer interactions while holding the average composition constant. It is shown that the thickness of the superlattice layers has a strong influence on the interlayer polar coupling, which in turn changes the phase transition. For the shortest periods studied (layers 5- and 10-nm thick) the onset of the phase transition is suppressed along with a significant broadening (as a function of $\mathrm{S}{\mathrm{m}}^{3+}$ concentration) of an incommensurately modulated phase determined by two-dimensional x-ray diffraction mapping. Consequently, a ferroelectric character with robust polarization hysteresis and enhanced dielectric constant is observed even for substitution concentration of $\mathrm{S}{\mathrm{m}}^{3+}$ which would otherwise lead to a leaky paraelectric in single-layer $(\mathrm{B}{\mathrm{i}}_{1\ensuremath{-}x}\mathrm{S}{\mathrm{m}}_{x})\mathrm{Fe}{\mathrm{O}}_{3}$ films. The experimental results are fully consistent with a mean-field thermodynamic theory which reveals that the strength of the interlayer coupling is strongly affected by the polar-polar interaction across the interface.

Effect of polar interactions on the structure and rheology of EVA/Montmorillonite nanocomposites

In this study we utilized X-ray diffraction, transmission electron microscopy (TEM) and various types of simple shear flow experiments to investigate the effect of the polar-polar interaction between ethylene-vinyl acetate co-polymers (EVA) and organo-silicates on the nanoscale structures and rheological properties of their melt blends. The WAXS intensities and TEM micrographs demonstrate that the exfoliation and the intercalation of nanoclays respectively prevail in EVA/Cloisite 30B nanocomposites and EVA/Cloisite 15A nanocomposites, respectively. The master curves obtained from transient shear flow tests and their Arrhenius plot demonstrate the formation of side-tethered structure in the melt blends of EVA/ Cloisite 30B nanoclay. Finally, by means of performing a series of large-strain relaxation tests and regression techniques, the single integral Wagner model, that is expected to appropriately describe the rheometric experiment data of melt blends, was established, and then a comparison of the calculated and measured viscosity and first normal stress is presented.

Dielectric relaxation of binary polar liquid mixture measured in benzene at 10 GHz frequency

The dielectric relaxation times τjk’s and dipole moments μjk’s of the binary (jk) polar liquid mixture of N,N-dimethyl acetamide (DMA) and acetone (Ac) dissolved in benzene (i) are estimated from the measured real σ′ijk and imaginary σ″ijk parts of complex high frequency conductivity σ*ijk of the solution for different weight fractions wjk’s of 0.0, 0.3, 0.5, 0.7 and 1.0 mole fractions xj of Ac and temperatures (25, 30, 35 and 40°C) respectively under 9.88 GHz electric field. τjk’s are obtained from the ratio of slopes of σ″ijk-wjk and σ′ijk-wjk curves at wjk → 0 as well as linear slope of σ″ijk-σ′ijk curves of the existing method (Murthy et al, 1989) in order to eliminate polarpolar interaction in the latter case. The calculated τ’s are in excellent agreement with the reported τ’s due to Gopalakrishna’s method. μjk’s are also estimated from slopes β’s of total conductivity σijk-wjk curves at wjk → 0 and the values agree well with the reported μ’s from G.K. method. The variation of τjk’s and μjk’s with xj of Ac reveals that solute-solute molecular association occurs within 0.0–0.3xj of Ac beyond which solute-solvent molecular association is predicted. The theoretical dipole moments μtheo’s are calculated from bond angles and bond moments to have exact μ’s only to show the presence of inductive, mesomeric and electromeric effects in the substituent polar groups. The thermodynamic energy parameters are estimated from ln(τjkT) against 1/T linear curve from Eyring’s rate theory to know the molecular dynamics of the system and to establish the fact that the mixture obeys the Debye-Smyth relaxation mechanism.

Relaxation phenomena of polar non-polar liquid mixtures under low and high frequency electric field

Simultaneous calculation of the dipole moment μj and the relaxation time τj of a certain number of non-spherical rigid aliphatic polar liquid molecules (j) in non-polar solvents (i) under 9.8 GHz electric field is possible from real e′ij and imaginary e″ij parts of the complex relative permittivity e*ij. The low frequency and infinite frequency permittivities e0ij and e∞ij measured by Purohitet al [1,2] and Srivastava and Srivastava [3] at 25, 35 and 30°C respectively are used to obtain static μs. The ratio of the individual slopes of imaginary σ″ij and real σ′ij parts of high frequency (hf) complex conductivity σ*ij with weight fractionsw jatw j → 0 and the slopes of σ″ij— σ′ij curves for differentw js [4] are employed to obtain τjs. The former method is better in comparison to the existing one as it eliminates polar-polar interaction. The hf μjs in Coulomb metre (C m) when compared with static and reported μs indicate that μs s favour the monomer formations which combine to form dimers in the hf electric field. The comparison among μs shows that a part of the molecule is rotating under X-band electric field [5]. The theoretical μtheos from available bond angles and bond moments of the substituent polar groups attached to the parent molecules differ from the measured μjs and μs to establish the possible existence of mesomeric, inductive and electromeric effects in polar liquid molecules.

Helix-helix packing and interfacial pairwise interactions of residues in membrane proteins

Helix-helix packing plays a critical role in maintaining the tertiary structures of helical membrane proteins. By examining the overall distribution of voids and pockets in the transmembrane (TM) regions of helical membrane proteins, we found that bacteriorhodopsin and halorhodopsin are the most tightly packed, whereas mechanosensitive channel is the least tightly packed. Large residues F, W, and H have the highest propensity to be in a TM void or a pocket, whereas small residues such as S, G, A, and T are least likely to be found in a void or a pocket. The coordination number for non-bonded interactions for each of the residue types is found to correlate with the size of the residue. To assess specific interhelical interactions between residues, we have developed a new computational method to characterize nearest neighboring atoms that are in physical contact. Using an atom-based probabilistic model, we estimate the membrane helical interfacial pairwise (MHIP) propensity. We found that there are many residue pairs that have high propensity for interhelical interactions, but disulfide bonds are rarely found in the TM regions. The high propensity pairs include residue pairs between an aromatic residue and a basic residue (W-R, W-H, and Y-K). In addition, many residue pairs have high propensity to form interhelical polar-polar atomic contacts, for example, residue pairs between two ionizable residues, between one ionizable residue and one N or Q. Soluble proteins do not share this pattern of diverse polar-polar interhelical interaction. Exploratory analysis by clustering of the MHIP values suggests that residues similar in side-chain branchness, cyclic structures, and size tend to have correlated behavior in participating interhelical interactions. A chi-square test rejects the null hypothesis that membrane protein and soluble protein have the same distribution of interhelical pairwise propensity. This observation may help us to understand the folding mechanism of membrane proteins.

Comparison of quantitative analytical methods in headspace gas chroamtography of residual solvents

The aim of this work was to compare quantitative methods used for headspace gas chromatographic analysis of residual solvents in standard aqueous solutions and to apply the methods to the analysis of medicines. We found that all three quantitative methods (external standard, ESTD; internal standard, ISTD; and standard addition, ASTD) enable determination of the total amount of solute in the equilibrated system by analysis of defined volumes of headspace gas. The results showed that the ISTD method is more precise than ESTD and ASTD when there is no strong interaction between the residual solvents and the pharmaceutical base material. When, however, there is a strong polarpolar interaction between them, the ESTD and ISTD methods give worse results than the ASTD method, because the ASTD method can eliminate the matrix effect.

Polar-Polar Interaction and Boundary Phase Structure Between Reinforcement and Matrix in a Polymer Composite

Abstract This paper describes an attempt to correlate the nature of polar-polar interaction between the reinforcement and matrix in a polymer composite with the boundary phase structure formed in contact with the reinforcement. It is shown by analyzing the mechanical dispersion data that the reinforcement-matrix interaction of Kevlar fiber reinforced poly(hydroxypropyl ether of bisphenol A) (P) is increased by blending poly(ethylene oxide) (E) or poly(ethylene adipate) (A) as a part of matrix, and that E is more efficient than A for the increase of the interaction. These results can be supported at the molecular level from the inspection of the Fourier transform infrared spectra on the Kevlar fiber coated with matrix polymers and the mixture of matrix polymers with benzanilide, which is used as a model compound of Kevlar fiber. It can be shown from the electron spectroscopy for chemical analysis on the films of PIE and P/A blend polymers formed on nylon 6 substrate (N), which is also used as a model material for the reinforcement, that A concentrates on the N-facing side for P/A film and that E concentrates on the air-facing side for PIE film. This result indicates the different susceptibility between P/A and PIE blends to the surface force from N, and hence, it likewise indicates the different interaction with the reinforcement in each blend, as shown by the mechanical dispersion data.

Approximate Formulas for the Viscosity and Thermal Conductivity of Gas Mixtures

Approximate expressions for the viscosity and thermal conductivity of gas mixtures have been derived from the rigorous kinetic theory formulas. Three levels of approximation are distinguished, with the third approximation rigorous for binary mixtures. The first approximation for mixture viscosity is found to be very nearly equivalent to empirical expressions known heretofore. The first and second approximations for mixture conductivity have been compared with rigorous calculations for binary mixtures of nonpolar gas pairs; the first approximation has an average error of 2.6% while the second approximation reduces this error to 0.5%. The second approximation accounts for the thermal conductivity of binary mixtures of polar and nonpolar gases. (It is assumed that the interchange of translational energy is abnormal for the polar-polar interaction.)