Effect of temperature on the intrinsic viscosity of poly(ethylene glycol) in water/dimethyl sulfoxide solutions

In this work, the intrinsic viscosities of poly(ethylene glycol) with molar mass of 20 kg mol^− 1 were measured in water/dimethyl sulfoxide solutions from (298.15 to 318.15) K. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The expansion factor were decreased by increasing temperature; therefore the chain of PEG shrinks and the end-to-end distance become smaller by increasing temperature. Perhaps the interactions of segment-segment are favored toward segment-solvent by increasing temperature; therefore the hydrodynamic volumes of the polymer coils become smaller by increasing temperature. The thermodynamic parameters (entropy of dilution parameter, the heat of dilution parameter, theta temperature and polymer-solvent interaction parameter) were derived by the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that the interactions of segment-segment were increased by increasing temperature.     

Lateral mobility of plasma membrane proteins in dividing eggs of the loach (Misgurnus fossilis): Regional differences and changes during the cell cycle

Regional differences in lateral diffusion rates of fluorescence-labeled proteins have been studied in the plasma membrane of dividing eggs of the loach (Misgurnus fossilis) by fluorescence recovery after photobleaching (FRAP). Apparent animal-vegetal differences in fluorescence intensity, lateral diffusion coefficients, and fractions of mobile proteins have been found, with all these quantities being higher in the animal pole region than in the yolk region. Cyclic changes in protein diffusion coefficients and mobile fractions during the first few cell cycles have also been recorded. Soon after the end of a cleavage, the diffusion coefficient reaches its minimal value and increases rapidly before the next cleavage.     

Comparative effects of alcohols (methanol,glycerol) and polyethylene glycol (PEG-300) on acid denatured state of goat liver cystatin

This report summarizes the effect of methanol, glycerol and polyol (PEG) on the acid induced state of goat liver cystatin by various spectroscopic techniques. Native goat liver cystatin (LC) has a fluorescence maximum at 340 nm, whereas the acid induced state shows a red shift of 15 nm with enhanced fluorescence intensity. Addition of 80% (V/V) methanol and glycerol both were found to stabilise the acid induced state of goat liver cystatin. However, glycerol was found to be a better stabilising agent than methanol. The unfolded state of liver cystatin obtained at pH 2 underwent a series of conformational changes when exposed to PEG-300 at varying concentrations. Tertiary structure was stabilized only at low concentrations of PEG-300 but higher concentrations resulted in the loss of tertiary structure.     

Molecular dynamics study on water self-diffusion in aqueous mixtures of methanol,ethylene glycol and glycerol: investigations from the point of view of hydrogen bonding

Molecular dynamics simulations have been performed to investigate the aqueous binary mixtures of alcohols, including methanol, ethylene glycol (EG) and glycerol of molalities ranging from 1 to 5 m at the temperatures of 273, 288 and 298 K, respectively. The primary purpose of this paper is to investigate the mechanism of water self-diffusion in water-alcohol mixtures from the point of view of hydrogen bonding. The effects of temperature and concentration on water self-diffusion coefficient are evaluated quantitatively in this work. Temperature and concentration to some extent affect the hydrogen bonding statistics and dynamics of the binary mixtures. It is shown that the self-diffusion coefficient of water molecules decreases as the concentration increases or the temperature decreases. Moreover, calculations of mean square displacements of water molecules initially with different number n of H-bonds indicate that the water self-diffusion coefficient decreases as n increases. We also studied the aggregation of alcohol molecules by the hydrophobic alkyl groups. The largest cluster size of the alkyl groups clearly increases as the concentration increases, implying the emergence of a closely connected network of water and alcohols. The clusters of water and alcohol that interacted could block the movement of water molecules in binary mixtures. These findings provide insight into the mechanisms of water self-diffusion in aqueous binary mixtures of methanol, EG and glycerol.     

A spectroscopic study of the coordination of dimethyl sulfoxide to a platinum (111) surface

Spectroscopic studies of the adsorption of dimethyl sulfoxide, (CH₃)₂S = O, on Pt(111) have shown that the molecule is bound to the surface via the sulfur atom in an inverted pyramid configuration. A comparison of XPS and EELS data for the adsorbed multilayer and monolayer with XPS and infrared data on the complex PtCl₂(DMSO)₂ is consistent with sulfur bonding. In addition, we detect a considerable increase of the v(S=O) frequency in the DMSO monolayer with decreasing coverage, indicating a coverage dependent heat of adsorption. UPS data show that on adsorption to form a monolayer, the highest occupied molecular orbital of DMSO, presumably the sulfur “lone pair” orbital, shifts to a higher binding energy. These results show a remarkable similarity between DMSO bonding to a metal surface and bonding to a single Pt²⁺ species.     

Effect of the shell on the transport properties of poly(glycerol) and Poly(ethylene imine) nanoparticles

Dendritic core–shell architectures containing poly (glycerol) and poly (ethylene imine) cores and poly(lactide) shell (PG-PLA and PEI-PLA respectively) were synthesized. Analogous of these core–shell architectures containing the same cores but poly (L-lactide) shell (PG-PLLA and PEI-PLLA, respectively) were also synthesized. In this work PG and PEI were used as macroinitiator for ring opening polymerization of the lactid and L-lactide monomers. Different molar ratios of monomer to end functional groups of PG ([LA]/[OH]) and PEI ([LA]/[NHn] (n = 1 or 2)) were used to prepare the core–shell architectures with different shell thickness. These core–shell architectures were able to encapsulate and transport the small guest molecules. Their transport capacity (TC) depended on the type and thickness of the shells. TC of core–shell architectures containing PLLA shell was higher than that for their analogs containing PLA shell. The diameter of core–shell architectures was between 20–80 nm. The rate of release of guest molecules from chloroform solution of nanocarriers to water phase was investigated and it depended on the type of the core, shell and solvent.     

Speeds of sound and isentropic compressibilities of (2-ethoxyethanol + ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol) binary mixtures at 298.15 K

The speed of sound (u) has been obtained at a frequency of 8.3 MHz in {CH₃CH₂OCH₂CH₂OH + HOCH₂CH₂(OCH₂CH₂)_nOH}for n = 0, 1, 2, and 3 over the whole composition range of studied binary liquid mixtures, at T = 298.15 K. The speed of sound values were combined with those of our previous results for densities and viscosities to obtain isentropic compressibility (κ_s), free volume (V_f), and intermolecular free length (L_f). From all these data excess isentropic compressibility (κ_s^E), excess free volume (V_f^E) and excess intermolecular free length (L_f^E) as well as the deviations of the speed of sound (Δu) were obtained. The results are interpreted in terms of molecular interactions occurring in the solutions.     

Poly(ethylene glycol) and phospholipid packing in the structure of reverse micelles

The influence of water substitution by a substance with a different polarity on the structure of phospholipid monolayer interface in water-in-oil microemulsion has been studied by the Fourier-transform pulsed-gradient spin-echo (FT PGSE)¹H nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spin-label methods. For this purpose the soybean phosphatidylcholine-based microemulsion and water soluble poly(ethylene glycol) with molecular weight 400 (PEG400) were used. Self-diffusion coefficients of all microemulsion components obtained by the FT PGSE NMR technique provided information about both the size of reverse micelles and distribution of components between different microemulsion compartments. The maximum hyperfine splitting, 2A _max, in the ESR spectra was used to characterize the degree of the phospholipid hydrocarbon chain mobility. It was shown that PEG400 alters significantly the size of the reverse micelles and the motion of the labeled segments of the lipid tails. A mechanism of PEG400 acting in solution of the phospholipid-based reverse micelles on the basis of the rough decrease of the micelle core polarity was suggested.     

Effect of pyrogallol-poly(ethylene glycol) on stabilization,structure, and interparticle potential of concentrated nickel nanoparticle suspensions

Nickel nanoparticles with an average diameter of 90 nm have been dispersed in de-ionized water with addition of pyrogallol-poly(ethylene glycol) polymers, hereafter termed Gallol-PEG, of different molecular weights as a surfactant. Measurement of zeta potential, infrared spectrum, and adsorption isotherm confirms the preferential anchoring from polar end of the surfactant molecules on the particle surface, forming a Langmuir-typed adsorption layer (adlayer) to provide an electrosteric stabilization. Concentrated nanoparticle suspensions with a solids loading up to 40 vol.% and an apparent viscosity lower than 10 Pa s at a shear rate of 100 s⁻¹ have been obtained, indicating that the Gallol-PEG adsorption is effective in facilitating the suspension flow under stress. The suspensions are yet fractal in structure with an experimentally determined fractal dimension of 2.1, revealing that a reaction-limited cluster–cluster aggregation is operative. This weakly coagulated fractal structure stems primarily from the shallow interparticle attraction operative over a moderate interparticle separation (~5–10 nm), and is prone to the adlayer thickness and the molecular conformation of the surfactant.     

Modelling the effect of methanol,glycol inhibitors and electrolytes on the equilibrium stability of hydrates with the SAFT-VR approach

In this work we integrate the statistical associating fluid theory for fluids interacting through potentials of variable range (SAFT-VR) into a traditional van der Waals and Platteeuw framework for modelling clathrate hydrates. We incorporate a new water–guest cell potential for the hydrate phase that can be related to the potential adopted in the familiar SAFT-VR equation of state for modelling fluids. We show how the ability of this equation of state to treat a wide range of complex fluids increases the scope of hydrate modelling to incorporate, in a single framework, the presence of various inhibitors (alcohols, glycols) or brines – or, indeed, any fluid for which a model is available (for use within SAFT-VR) or can be conveniently obtained. Agreement with experimental results is good throughout and, in many cases, excellent.     

Effect of poly (ethylene glycol) coating on the magnetic and thermal properties of biocompatible magnetic liquids

The aim of this study was to investigate the influence of poly(ethylene glycol) surface-active coating on the magnetic and thermal properties of biocompatible magnetic liquids. The data were analyzed using the high-temperature approximation model taking into account polydispersity of a system. Heating ability of the PEG-stabilized magnetic fluids was determined by the calorimetric measurement of specific absorption rate (SAR) at a frequency of 750 kHz and a magnetic field of 0-2 kA/m. MF-Oleate/PEG heating properties were found to be comparable to the ones of MF-Oleate. The PEG shell thus does not seem to effect the thermal characteristics and SAR values and might make the magnetic fluid useful for application in hyperthermia treatment.     

Self-assembly of silanated poly(ethylene glycol) on silicon and glass surfaces for improved haemocompatibility

Surface immobilization of poly(ethylene glycol) (PEG) is an effective method to produce a material surface with protein repulsive property. This property could be made permanent by using covalent grafting of the PEG molecules onto material surfaces. In this study, self-assembled monolayers (SAMs) of PEG on silicon-containing materials (silicon chip and glassplate) were obtained through a one-step coating procedure of one kind of silanated PEG molecules made through the reaction between monomethoxy PEG and 3-isocyanatopropyltriethoxysilane. Atomic force microscopy (AFM) and water static contact angle measurement were employed to investigate the surface topography and wettability of the PEGylated material surfaces. The changes in the topography and the water contact angle of the surfaces with time of incubation in PBS solution were also measured. The results revealed that stable and uniform self-assembled monolayers of PEG could be formed on silicon or glass surfaces by simply soaking the substrates in the solution of silanated PEGs. The covalent coupling of PEGs to the substrates was also confirmed. In order to evaluate the stability of the SAMs, blood compatibility of the modified glassplate surface was evaluated by measuring full blood activated partial thromboplastin time (APTT), prothrombin time (PT), and thrombin time (TT), as well as by scanning electron microscopy (SEM) analysis of the appearance of adherence and denaturation of blood platelets onto the glassplate. The silanated PEGs were shown to have good effect on the protein-repulsion as well as haemocompatibility of the substrates.     

Polymer electrolytes based on copolymer of poly(ethylene glycol) dimethacrylate and imidazolium ionic liquid

Polymer electrolytes based on the copolymer of N-vinylimidazolium tetrafluoroborate (VyImBF₄) and poly(ethylene glycol) dimethacrylate (PEGDMA) have been prepared. Ethylene carbonate (EC) and LiClO₄ are added to form gel polymer electrolytes. The chemical structure of the samples and the interactions between the various constituents are studied by FT-IR. TGA results show that these polymer electrolytes have acceptable thermal stability, are stable up to 155 °C. Measurements of conductivity are carried out as a function of temperature, VyImBF₄ content in poly(VyImBF₄-co-PEGDMA), and the concentration of EC and LiClO₄. The conductivity increases with PEGDMA and EC content. The highest conductivity is obtained with a value of 2.90 × 10^? 6 S cm^? 1 at room temperature for VP1/EC(25 wt.%)–LiClO₄ system, corresponding to the LiClO₄ concentration of 0.70 mol kg^? 1 polymer.     

Reactions of methanol and ethylene glycol on Ni/Pt: Bridging the materials gap between single crystal and polycrystalline bimetallic surfaces

The catalytic decompositions of methanol and ethylene glycol on polycrystalline Ni/Pt surfaces were used as model probe reactions to explore oxygenate reforming for H₂ production. In the current study we evaluated whether favorable chemistry observed on single crystal Ni/Pt(111) can be extended to more commercially relevant polycrystalline surfaces, thus bridging the “materials gap”. Auger electron spectroscopy (AES) confirmed that two distinct bimetallic configurations can be formed for the Ni/Pt system, each possessing unique chemical properties: one with the surface enriched in Ni atoms, designated NiPtPt, and the other with the subsurface region enriched in Ni atoms, designated PtNiPt. Consistent with single crystal studies, temperature programmed desorption (TPD) revealed that the NiPtPt configuration was more active for reforming to CO and H₂ than either polycrystalline Pt or PtNiPt. High-resolution electron energy loss spectroscopy (HREELS) confirmed the presence of strongly bound reaction intermediates on NiPtPt, including aldehyde-like species, which was also observed on Ni–Pt–Pt(111). The strongly bound reaction intermediates most likely contribute to the high reforming activity observed on NiPtPt. Overall, TPD and HREELS results on polycrystalline surfaces were in general consistent with their single crystal counterparts for the reforming of oxygenates.     

The Effect of Hydrophilic Bentonite Nanoclay on the Thermogelation Properties of Poly(N-isopropylacrylamide)-poly(ethylene glycol)-poly(N-isopropylacrylamide) Triblock Copolymer Aqueous Solutions

The effect of hydrophilic bentonite addition on the thermogelation properties of aqueous solutions of poly(N-isopropylacrylamide)–poly(ethylene glycol)–poly(N-isopropylacrylamide) (PNIPAM-PEG-PNIPAM) triblock copolymers of various compositions and molecular weights was investigated. Dynamic rheometry and differential scanning calorimetry (DSC) measurements showed that increasing concentrations of clay added to 20 wt.% polymer aqueous solutions caused a decrease of the temperature at which the viscosity starts increasing, while the temperature corresponding to the maximum endothermic effect due to the PNIPAM chain dehydration remained practically unchanged. The storage modulus, G′, increased with clay concentration for shorter PNIPAM chain triblock copolymers, while an opposite situation occurred in the case of the block copolymer with the longest PNIPAM block. For bentonite concentrations above 1 wt.%, G′ was larger than the viscous modulus, G″, at temperatures higher than the phase separation temperature, indicating a predominantly elastic character of the resulting composite hydrogels. These findings were explained through the presence of polymer–clay interactions occurring mainly through the PEG blocks.     

Rotational, internal rotational, and translational motion of acetic acid and dimethyl sulfoxide in their liquid mixture (with some results for DMSO dissolved in MeOH)

The proton magnetic relaxation rate of DMSO in the mixture 33.3 mole % DMSO + 66.7 mole % CD₃COOD has been measured in the temperature range 3.5 < 1000/T < 6.0 K and at six frequencies 6 < ν < 144 MHz. The intramolecular relaxation rate was determined by the aid of the isotopic substitution technique. The rotational correlation time of “the molecule” and the time constant of the internal motion have been extracted from these experimental results. The corresponding measurements were also performed on DMSO in the solvent CD₃OD (71 mole %) where no internal motion effect appeared in the temperature dependence of the relaxation rate. Furthermore, proton relaxation rates of the acetic acid methyl group and deuteron relaxation rates of the acid methyl and OD group are reported. Again, the data are given in the temperature range as above and for a number of frequencies. Rotational time correlation functions g(t) for the axid molecule are derived. Finally we present experimental results for the self-diffusion coefficients of both mixture partners DMSO and AcH and of DMSO in the solvent MeOH.     

The adsorption and reaction of ethylene glycol and 1,2-propanediol on Pd(111): A TPD and HREELS study

The reactions of ethylene glycol and 1,2-propanediol have been studied on Pd(111) using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). Both molecules initially decompose through O–H activation, forming ethylenedioxy (–OCH₂CH₂O–) and 1,2-propanedioxy (–OCH₂CH(CH₃)O–) surface intermediates. For ethylene glycol, increases in thermal energy lead to dehydrogenation and formation of carbonyl species at both oxygen atoms. The resulting glyoxal (O═CHCH═O) either desorbs molecularly or reacts through one of two competing pathways. The favored pathway proceeds via C–C bond scission, dehydrogenation, and decarbonylation to form carbon monoxide and hydrogen. In a minor pathway, small amounts of glyoxal undergo C–O bond scission and recombination with surface hydrogen to form ethylene and water. The same reaction mechanism occurs for 1,2-propanediol after methyl elimination and formation of glyoxal. However, this is accompanied by a minor pathway involving a methylglyoxal (O=CHC(CH₃)=O) intermediate. The prevalence of the dehydrogenation/decarbonylation pathway in the current work is consistent with the high selectivity for C–C scission in the aqueous phase reforming of polyols on supported Pd catalysts.     

Small-angle neutron scattering studies on water soluble complexes of poly(ethylene glycol)-based cationic random copolymer and SDS

The interaction of cationic random copolymers of methoxy poly(ethylene glycol) monomethacrylate and (3-(methacryloylamino)propyl) trimethylammonium chloride with oppositely charged surfactant, sodium dodecyl sulphate, and the influence of surfactant association on the polymer conformation have been investigated by small-angle neutron scattering. SANS data showed a positive indication of the formation of RCPSDS complexes. Even though the complete structure of the polyion complexes could not be ascertained, the results obtained give us the information on the local structure in these polymer-surfactant systems. The data were analysed using the log-normal distribution of the polydispersed spherical aggregate model for the local structure in these complexes. For all the systems the median radius and the polydispersity were found to be in the range of 20 ± 2 Å and 0.6 ± 0.05, respectively.     

双(2,2-二硝基丙基)甲缩醛的结构和爆轰性能的量子化学研究

利用B3LYP/6-311+G(2d,p)方法对一种新型含能增塑剂双(2,2-二硝基丙基)甲缩醛进行几何优化,计算了其红外光谱、生成焓和爆轰特性. 分析了最弱键的键离解能和键级并预测了目标化合物的热稳定性. 结果表明双(2,2-二硝基丙基)甲缩醛中的四个N-NO₂键的键离解能都为164.38 kJ/mol. 表明目标化合物是一个热力学性能稳定的化合物. 以凝聚相生成焓和分子密度为基础,采用Kamlet-Jacobs方法预测其爆速和爆压. 目标化合物的晶体结构属于P21空间群.