Heat-treated magnesia as an adsorbent for the class separation of aliphatic monocarbonyl compounds

In order to control the activity of magnesia as an adsorbent, the effect of temperature was studied. The activity of various temperature of treatment showed two regions. During the first, in the range 106–320°, the activity increased with increasing temperature, whereas at temperatures above 320° the activity decreased with increasing temperature.The iodine number of heat-treated magnesia correlated well with its affinity for 2,4-dinitrophenylhydrazones of carbonyls.By heating several batches of magnesia at graphically determined temperatures. it was possible to obtain adsorbents with the same activity for class separation.     

Transesterification,morphology and some mechanical properties of thermotropic liquid crystal polymers/polycarbonate blends

Blends of polycarbonate (PC) and thermotropic liquid crystal polymer Vectra-A (VA), with up to 20 wt.% VA were prepared at temperatures up to 320°C. Transesterification (TE) was found to take place notably at the highest blending temperature. At this temperature, it increased linearly with the VA content. TE products, located at PC/VA interfaces led to reductions in the size of dispersed phase droplets, as shown by scanning electron microscopy. The inference of increased compatibility was consistent with improvements in mechanical property parameters of the blends. These also showed that mixing time was a factor in defining interfacial states. Acid–base interaction data gave further evidence of the presence of TE products, notably when blending occurred at 320°C, and suggested that ∼10 wt.% of VA was needed to saturate interfaces with PC. The absolute values of acid and base interaction constants were found to be very low, confirming earlier evidence that near 320°C dispersion forces are dominant at PV/VA interfaces, contributing to enhanced compatibility in blends prepared at these high temperatures.     

Tunable blood compatibility of polysulfobetaine from controllable molecular-weight dependence of zwitterionic nonfouling nature in aqueous solution

This work describes a tunable blood compatibility of zwitterionic poly(sulfobetaine methacrylate) (polySBMA) polymers at a wide range of high molecular weights from 50 kDa to 300 kDa controlled with a similar polydispersity via homogeneous free-radical polymerization. The control of molecular weights of polySBMA highly regulates the zwitterionic nonfouling nature to resist the adsorption of plasma proteins, the coagulant of human plasma, and the hemolysis of red blood cells. In this study, the upper critical solution temperatures (UCSTs) and hydrodynamic size of prepared polymers are determined to illustrate the correlations between intermolecular zwitterionic associations and blood compatibility of polySBMA suspension in human blood. The polySBMA exhibited clear shifts of UCSTs in the stimuli-responsive control of solution pH and ionic strength, which were strongly associated with the molecular weights of the prepared polymers. Plasma-protein adsorption onto the polySBMA polymers from single-protein solutions and the complex medium of 100% human plasma were measured by dynamic light scattering to determine the nonfouling stability of polySBMA suspension. It was found that the nonfouling nature as well as hydration capability of polySBMA can be effectively controlled via regulated molecular weights of zwitterionic polymers. This work shows that the polySBMA polymer with an optimized molecular weight of about 135 kDa at physiologic temperature is presented high hydration capability to function the best nonfouling character of anticoagulant activity and antihemolytic activity in human blood. The excellent blood compatibility of zwitterionic polySBMA along with their stimuli-responsive phase behavior in aqueous solution suggests their potential for use in blood-contacting targeted delivery and diagnostic applications.     

The embedded atom model of liquid cesium

The embedded atom potential was calculated for cesium over the temperature range 323–1923 K at pressures up to 9.8 GPa from the diffraction data on the structure of the metal close to the temperature of fusion (T _f). The parameters of the embedded atom potential were adjusted using the data on the thermodynamic properties and structure of liquid cesium. The embedded atom potential well predicts the structural and thermodynamic characteristics of the liquid metal as the temperature increases along the liquid-vapor equilibrium line and under strong compression. The calculated potential energy and structure of liquid cesium closely agree with the experimental data at temperatures up to 1373 K. The calculated bulk compression modulus is close to its experimental values at all temperatures except 323 K. The self-diffusion coefficients increase as the temperature grows by a power law with an exponent close to 2 and satisfy the Stokes-Einstein equation. Deviations from experimental data at temperatures above 1400 K are explained by the metal-nonmetal transition that occurs as the density decreases.     

聚氨酯硬链段球晶生长与软硬链锻混容性的关系

线型可溶性聚氨酯的硬链段结晶难以长成球晶 ,然而本实验室已经证明即使从熔体结晶硬链段也是能够长成球晶的 .研究了聚酯与聚醚型聚氨酯硬链段长球晶的规律 ,并发现聚氨酯硬链段长球晶的难易与聚氨酯软硬链段混容性密切相关 .动态力学分析 (DMA)与示差扫描量热 (DSC)实验表明聚ε 已内酯 (PCL)、聚已二酸丁二醇酯 (PTMA)、聚四氢呋喃 (PTMO)及聚环氧丙烷 (PPO)型聚氨酯的软硬链段混容性从前至后递减 .从熔体退火结晶时 ,聚氨酯硬链段长成球晶的退火温度范围是有限的 ,软硬链段混容性越好 ,聚氨酯硬链段能长成球晶的温度范围越窄 ,所需长的时间越长 .聚氨酯硬链段长球晶的下限温度取决于软硬链段间所存在的氢键作用 ,聚氨酯硬链段长球晶的上限温度与软硬链段混容性直接相关 .     

Preformulation compatibility studies of etamsylate and fluconazole drugs with lactose by DSC

Chemical compatibility of two drugs, namely, etamsylate and fluconazole was studied with lactose as excipient, employing differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. The DSC patterns recorded for the mixtures of both the drugs with the common excipient (lactose) indicated that fluconazole as well as etamsylate were incompatible with lactose at high temperatures. X-ray diffraction patterns recorded for pure drugs and lactose and the mixtures of individual drugs with lactose prepared at room temperature by intimate grinding of the components revealed incompatibility of both the drugs with lactose also at room temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetcis and mechanism of HCN-evolution from the oxidation of polyurethanes

The oxidative degradation of aliphatic, aromatic, and secondary polyurethanes was investigated over a range of temperatures of 440–1000°C as a function of time and oxygen concentration. The degradation was studied with special emphasis on HCN-evolution; its rate constants and Arrhenius equations were determined. In some of the temperature ranges reactions were diffusion controlled. At relatively low temperatures the oxidative rate constant was a linear function of oxygen concentration, whereas at higher temperatures oxidation of the evolved HCN took place in passage through the hot zone of the furnace; in addition, at these higher temperatures thermal degradation of the polymers and thermal decomposition of HCN in the hot zone occurred simultaneously with oxidation to an appreciable extent. The kinetics and mechanism proposed and quantitatively evaluated account well for the experimental results.     

Influence of temperature on peak shape and solvent compatibility: implications for two-dimensional liquid chromatography

Solvent compatibility is a limiting factor for the success of two-dimensional liquid chromatography (2-D LC). In the second dimension, solvent effects can result in overpressures as well as in peak broadening or even distortion. A peak shape study was performed on a one-dimensional high-performance liquid chromatography (HPLC) system to simulate the impact of peak distorting solvent effects on a reversed-phase second dimension separation operated at high temperatures. This study includes changes in injection volume, solute concentration, column inner diameter, eluent composition and oven temperature. Special attention was given to the influence of high temperatures on the solvent effects. High-temperature HPLC (HT-HPLC) is known to enhance second dimension separations in terms of speed, selectivity and solvent compatibility. The ability to minimise the viscosity contrast between the mobile phases of both dimensions makes HT-HPLC a promising tool to avoid viscosity mismatch effects like (pre-)viscous fingering. In case of our study, viscosity mismatch effects could not be observed. However, our results clearly show that the enhancement in solvent compatibility provided by the application of high temperatures does not include the elimination of solvent strength effects. The additional peak broadening and distortion caused by this effect is a potential error source for data processing in 2-D LC.     

聚己内酯和聚氧化乙烯共混体系中的两类片晶相间堆砌

对聚(ε-己内酯)(PCL)/聚氧化乙烯(PEO)共混物的相差显微镜、广角X-射线衍射(WAXD)、小角X-射线散射(SAXS)及示差扫描量热计(DSC)等的研究表明,只有当共混物中PCL(或PEO)的含量低于20％时,两组份是相容的.当PCL含量低于20％时,在共混物中形成了PEO片晶和PCL片晶相间堆砌的结晶形态,当PEO含量不超过20％时,PEO则完全以非晶形式混入PCL的非晶区,同时阻碍了PCL的结晶.可见在结晶过程中,相容的两组份对共混体系形态结构的影响却不尽相同.     

Helical twisting power and compatibility in twisted nematic phase of new chiral liquid crystalline dopants with various liquid crystalline matrices

ABSTRACT

Four chiral dopants exhibiting smectic LC phases themselves were prepared and their helical twisting power (HTP) and thermal phase behaviour in mixtures with four various LC hosts were studied. The influence of host liquid crystal on HTP was evaluated and generally higher values were found for hosts with high birefringence. Unexpectedly, high enhancement was found for an LC-chiral dopant pair, both having a similar aromatic core – biphenyl ring substituted with polar group. All studied chiral dopants exhibited limited compatibility with the LC hosts in twisted nematic phase at room temperature. For one of the studied mixtures, it was able to obtain single twisted nematic phase with selective light reflection band with maximum at wavelength about 1.0 µm. Carboxylic acid-type dopants exhibited total compatibility with the studied host in single twisted nematic phase at elevated temperatures, allowing preparation of mixtures with reflection band in the visible range. In case of the carboxylic acid dopants, blue phases for optimised compositions were observed. Intermolecular hydrogen bonding between carboxylic acid proton and pyridine nitrogen of chiral dopants was found. Doping the LC host with these dopants led to slight enhancement of HTP value and higher solubility in the LC host.     

Temperature dependence of the rate of formation of active species in nanosecond streamer corona discharge between a solid electrode and water surface

The dependence of the yield of ozone in a nanosecond streamer electric corona discharge in the presence of oxygen and water vapor on temperature over the range 25–66°C was examined. It was found that the yield decreased to zero with an increase in temperature to 66°C. The decrease in the yield can be explained in terms of an increase of water vapor concentration in the discharge gap at elevated temperatures, as well as by an increase in the water ionization constant.     

Thermally reversible light scattering films based on the melting/crystallization of organic crystals dispersed in an epoxy matrix

Films that can be reversibly switched from opaque to transparent states by varying temperature (TRLS films), have potential applications in thermal sensors, optical devices, recording media, etc. A dispersion of organic crystals in a thermoset may be used for these purposes provided that at temperatures higher than the melting point there is a matching of refractive indices of both phases. A model system consisting on a dispersion of diphenyl (DP) crystals in an epoxy matrix based on diglycidyl ether of bisphenol A and m-xylylenediamine, was analyzed as a possible TRLS film encapsulated between transparent covers to avoid sublimation of DP. To obtain a uniform dispersion of DP-rich domains in the epoxy matrix by polymerization-induced phase separation, it was necessary to add 5 wt% of polystyrene (PS) to the initial formulation. Phase separation induced by polymerization at 80 °C led to a dispersion of PS/DP domains in the epoxy matrix due to the low compatibility of PS with the epoxy and its high compatibility with DP. Crystallization and melting processes were confined to the interior of dispersed domains leading to an excellent reproducibility of the optical properties of TRLS films in the course of successive heating-cooling cycles.     

Single-Phase Polymer Alloys of Polyvinyl Chloride and New Polymers

Polymer alloying is acquiring ever increasing significance for the modification of polymeric materials. Polymer alloys are defined by their phase character, which in turn is determined by the mutual compatibility or incompatibility of the components. Suitable techniques for the analysis of the phase character include, inter alia, dynamic-mechanical methods, according to which a polymer alloy may be considered in a simplified manner as single-phase when only one glass transition is observed, even if it extends over a broader temperature range than in the case of the pure components. Aliphatic (polyester)-polycarbonates and tetramethylbisphenol-A polycarbonate are new, PVC-compatible, polymer modifiers. The (polyester)-polycarbonates (from adipic acid, hexane-1,6-diol, neopentanediol, and diphenyl carbonate) yield with PVC single-phase alloys that at temperatures above the glass transitions of the mixture display the characteristics of soft PVC and that are tough far below this temperature. The special high-temperature properties of the resin-like tetramethylbisphenol-A polycarbonate permits the preparation of alloys with increased dimensional stability under heat (higher deflection temperatures under load).     

Studies of molecular relaxation of poly(propylene oxide) solutions by dielectric relaxation and brillouin scattering

Dielectric relaxation and Brillouin scattering are jointly used in studying molecular relaxation in poly(propylene oxide) (PPO) and its solutions in methylcyclohexane. The dielectric method was applied to the more concentrated (100%, 80%, 60%, by volume) solutions over a wide temperature and frequency range (30 Hz to 8 GHz) in order that the variation in activation energy characteristic of a glass-forming substance could be delineated. The present work extends previous work on the undiluted polymer to higher frequencies so that range of 12 decades in the dielectric loss maximum f_max as a function of temperature is now available. The “Antoine” equation is found to represent the behavior of log f_max, of the bulk concentrated solutions very well. The more dilute (40%, 20%) solutions were studied only in the high-frequency (GHz) region since phase separation occurred at low temperatures. Both the temperature and dilution effects were interpreted in terms of free-volume theory. Brillouin scattering spectra were obtained at several scattering angles and a wide range of temperatures. A maximum in the curve of hypersonic attenuation versus temperature was observed in each polymer solution. The attenuation maximum shifts toward lower temperature upon dilution, in agreement with the dielectric relaxation result. The Brillouin scattering follows different activation parameters and evidences a more rapid process than does the dielectric relaxation. It is speculated that it monitors a secondary or subglass relaxation, due perhaps, to damped torsional oscillations.     

Detection of compatibility of some rubber blends by DSC

The compatibility of some technically important polymer blends, namely BR/NR, NR/NBR and CR/NBR, has been investigated using the DSC method. In addition, dynamic mechanical measurements have been carried out for the NR/NBR blends over the frequency range of 10^–4 Hz –200 Hz and temperatures ranging from –70 to +70°C.The results obtained show that the three rubber blends are not compatible over the entire composition range as proven by the DSC and mechanical measurements. By analyzing the heat capacity increases at the glass transitions of the separate phases in the NR/BR blend, it was possible to suggest the presence of a limited compatibility at the boundaries of the two phases.By comparing this work with prior measurements, it was possible to conclude that the calorimetric method is a more efficient tool for the study of compatibility of polymer blends when compared to ultrasonic and viscosity methods.Furthermore, it was found that polymers that show compatibility when measured with an ultrasonic method could behave compatible, semicompatible or incompatible when analyzed by DSC. On the other hand, blends that show incompatibility by the ultrasonic method are always incompatible by the DSC method.Dedicated to Professor Wunderlich on the occasion of his 65th birthdayWe are grateful to Prof. Dr. W. Pechhold for stimulating and promoting this work and thanks due to colleagues at the Department of Applied Physics and Section of Calorimetry, Ulm University for their valuable help. Thanks are also extended to Alexander von Humboldt Foundation for supporting the residence of A. A. Yehia in Ulm, which gave the starting impulse to this work. A. Mansour. would like to thank the USAID for supplying the PL-DSC to the Chemistry Dept., Cairo University.     

Use of isothermal microcalorimetry in pharmaceutical preformulation studies

Excipient compatibility of a new chemical entity was assessed using an isothermal microcalorimeter. Mixtures of an active pharmaceutical ingredient with a primary amine group and excipients were prepared in a 1:1 ratio and compatibility monitored by exposing to 50, 60 and 70°C in presence of 200 mL of water. The new chemical entity, a primary amine, reacted with reducing sugars such as lactose and resulted in a brown discoloration. This reaction is the Maillard type condensation reaction between amines and reducing sugars. The rate of reaction was dependent on the temperature with rapid degradation at higher temperatures. No other incompatibility was apparent between the primary amine and other excipients This revised version was published online in July 2006 with corrections to the Cover Date.     

Liquid water confined in carbon nanochannels at high temperatures

Structure, hydrogen bonding, electrostatics, dielectric, and dynamical properties of liquid water confined in flat graphene nanochannels are investigated by molecular dynamics simulations. A wide range of temperatures (between 20 and 360 degrees C) have been considered. Molecular structure suffers substantial changes when the system is heated, with a significant loss of structure and hydrogen bonding. In such case, the interface between adsorbed and bulk-like water has a marked tendency to disappear, and the two preferential orientations of water nearby the graphite layers at room temperature are essentially merging above the boiling point. The general trend for the static dielectric constant is its reduction at high temperature states, as compared to ambient conditions. Similarly, residence times of water molecules in adsorbed and bulk-like regions are significantly influenced by temperature, as well. Finally, we observed relevant changes in water diffusion and spectroscopy along the range of temperatures analyzed.     

The effect of ion aggregation on some melt properties of styrene ionomers

The dynamic modulus, G′, and viscosity, η′, in the melt were determined for styrene ionomers containing up to 7.7 mole-% sodium methacrylate in the frequency range of 10^?2 to 40 rad/sec, at various temperatures. The same parameters were determined for the methyl ester of these ionomers, as well as for some acid samples. It was found that in the temperature range studied the time–temperature superposition principle was applicable to the salts as well as to the esters and acids. Furthermore, it was found that the shapes of the G′ versus ω plots for the three types of polymers were identical for a particular molecular weight and comonomer concentration, and independent of whether the sample was in the acid, ester, or salt form. The temperatures required to achieve superposition were, however, quite different. This temperature difference, ΔT (between the salt and the ester), was found to be a function of the ion concentration, c. The shape of the plot of ΔT versus c suggests that the structure of the ionic aggregates changes in the range of 4–5 mole-% of ions.     

Super-Toughened Heat-Resistant Poly(lactic acid) Alloys By Tailoring the Phase Morphology and the Crystallization Behaviors

The interfacial grafting copolymerization and the compatibility between poly(lactic acid) (PLA) and ethylene-vinyl acetate-glycidyl methacrylate elastomer (EVM-GMA) are adjusted by varying the blending temperatures. High temperature is favored to the grafting reaction between epoxy groups of the EVM-GMA and terminal groups of the PLA, resulting in better compatibility between the two components. Taking PLA/EVM-GMA (80/20) blend as an example, an increase in blending temperature from 175 to 230 °C led to a 42.8% reduction in EVM-GMA particle size, and consequently 137.8% and 52.6% increases in elongation at break (Eb) and notched impact strength (NIS), respectively. In comparison, the Eb and NIS of PLA/EVM blends without any interfacial reaction deteriorated dramatically due to thermal degradation of the PLA at high(er) temperatures. Furthermore, the PLA/EVM-GMA blend prepared at 230 °C possesses both excellent toughness (Eb > 60%, NIS > 60 kJ m⁻²) and high heat deflection temperature (>90 °C) after annealing at 100 °C. This work provides a new approach in designing high-performance biobased materials which may broaden the application range of PLA in engineering areas. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 500–509     

Temperature‐dependent polymer–polymer interactions in polystyrene–polyethylene blends

The effect of the temperature on the interaction between the components of an immiscible polystyrene–polyethylene blend has been analyzed with different techniques. Lap‐shear‐strength data and morphological observations indicate an enhanced interaction between the polymeric phases at elevated temperatures, at which dispersive forces are known to predominate. This raises the degree of compatibility of the polymeric components. Rheological measurements also justify the concept of increased adhesion between the components of the blend when it is processed at very high temperatures. Differential scanning calorimetry analysis lends support to an improved homogeneity of the blend at an elevated temperature; this is again consistent with an improved interaction between the blend phases. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2545–2557, 2004