Influence of temperature on surface tension of three liquid crystal polymers and polyethylene terephtalate

In this work Pressure Volume Temperature (PVT) data for three different liquid crystal polymers (LCPs), namely Vectra A950^® and two LCPs based on 4,4'-dihydroxybiphenyl (PB-n) (where n is the number of methylene units present in the polymer) and polyethylene terephtalate (PET), were obtained for temperatures ranging from 50 to 300°C and pressures ranging from 0.1 to 200 MPa. The experimental data were fitted to the Flory-Orwoll-Vrij equation of state and used to predict the influence of temperature on the surface tension of the four materials studied.

The surface tension of PET was shown to decrease linearly with increasing temperature. The surface tension of both PB-11 (γ_PB-11) and Vectra A950^® (γ_Vectra) decreased linearly with increasing temperature for temperatures corresponding to the nematic phases of the materials. Abnormal behaviour was observed for the surface tension of PB-8 (γ_PB-8): at temperatures just above T_b (the temperature at which the material became birefringent), γ levelled off and then decreased. A clear discontinuity was observed for both γ_PB-8 and γ_PB-11 near the mesophase to isotropic transition. For both PB-8 and PB-11, γ decreased linearly with increasing temperature for temperatures corresponding to the isotropic phases of the materials.     

Surface tension of pure liquid lanthanide and early actinide metals

A systematic theoretical study of the surface tension of liquid rare earth metals and early actinides is performed. An equation, based on the theoretical considerations suggested by Eyring, enables one to calculate the surface tension of elementary substances in a wide temperature range from melting to boiling points. The results of temperature-dependent surface tension calculations of a pure liquid terbium (1629–1880?K) are fitted as γ?=?845?0.1 (T???T _m) (mJ?m²), where the surface tension decreases linearly with temperature. The surface tension was also calculated, at melting points, for all the liquid rare earth metals from La to Lu and for the first six metals of the actinide series from Ac to Pu. It is observed that the lanthanides may be divided into three groups in accordance with their electronic structure. Mostly, the calculated results agree well with available experimental data.     

Thermally stimulated current and DSC studies of the broadened glass transition in liquid crystalline polymers

The high sensitivity of the thermally stimulated current, thermal sampling (TS) method is emphasized in a study of the breadth of the glass transition in several liquid-crystalline polymers (LCPs). Differential scanning calorimetry (DSC) was performed on all samples to further quantify the glass transition regions. For “random” copolyester LCPs with widely varying degrees of crystallinity, including highly amorphous samples, very broad glass tran-sition regions were observed. One semicrystalline alternating copolyester and a series of semicrystalline azomethine LCPs were studied as examples of structurally regular polymers. These exhibited relatively sharp glass transitions more comparable to ordinary isotropic amorphous or semicrystalline polymers. The broad glass transitions in the random copolyesters are attributed to structural heterogeneity of the chains. In one example of a moderate-crystallinity random copolyester LCP (Vectra), glass transitions ranging up to ca. 150°C in breadth were determined by the thermal sampling (TS) method and DSC. In other lower crystallinity copolyester LCPs, the main glass transition temperature as determined by DSC was comparable to that determined by TSC although cooperative relaxations of a minor fraction of the overall relaxing species were detected well below the main T_g, by the TS method and not by DSC. Rapid quenches from the isotropic melt to an isotropic glass were possible with one LCP. The anisotropic and isotropic glassy states for this LCP were found to have the same breadth of the glass transition as was determined by the TS method, although TSC and DSC show that T_g is shifted downward by ca. 15°C in the anisotropic glass as compared to the isotropic glass. © 1993 John Wiley & Sons, Inc.     

Study of the surface and interfacial tensions in systems containing a low molar mass liquid crystal

The surface tension of a low molar mass liquid crystal (LMMLC), 4-cyano-4'-n-heptyloxybiphenyl (70CB), was measured as a function of temperature using the pendant drop method, forming drops of different volumes ranging from 5 to 11 mm³. Contact angles formed by drops of 70CB in the nematic and isotropic phases on plates of polystyrene (PS) and of a liquid crystal polymer (LCP), VECTRA A910, were also measured. Only large drops could be used for surface tension analysis. It was shown that in the nematic phase the surface tension of 70CB decreases with increasing temperature, and that in the isotropic phase the surface tension increases with increasing temperature. Using the values of contact angle and of surface tension of 7OCB it was possible to evaluate the interfacial energy between 7OCB and PS and between 7OCB and VECTRA. The interfacial energy between 7OCB and PS, and between 7OCB and VECTRA, decreased with increasing temperature for ranges of temperatures corresponding to both phases of 70CB.     

尼龙6/液晶聚合物共混体系中化学反应对体系热行为及形貌的影响

采用漫反射红外光谱法(DRIFT)和示差扫描量热法(DSC)研究了2种不同特性黏数的尼龙6与3种液晶聚合物(Vectra A950、Vectra B950和Rodrun LC5000)之间的酯-酰胺交换反应.DRIFT测试证实了尼龙6与LC5000之间存在化学反应.DSC分析表明,酯-酰胺交换反应使体系中尼龙6的熔点下降、结晶度降低.增加反应时间和增大共混体系中液晶聚合物的含量有利于酯-酰胺交换反应的发生.与Vectra A950和Vectra B950相比,分子链柔性较强的Rodrun LC5000与尼龙6之间的化学反应更容易进行.扫描电子显微镜(SEM)观察表明,随着共混时间的延长,分散相形貌由球状粒子发展为短棒状纤维,乃至最终形成直径更细的微纤结构.     

The liquid–gas interface of oxygen–nitrogen solutions: 1. Surface tension

The capillary method of surface tension measurement has been used to measure the surface tension of oxygen–nitrogen solutions in the temperature range from 80 to 132 K. At temperatures below the nitrogen critical temperature (T_c = 126.2 K) the capillary constant and the surface tension of solutions are smaller than their additive values and vary linearly with the temperature. Experimental data are compared with the results of calculating the surface tension by the theories of Pinnes and Rowlinson.     

Physicochemical properties of {1-methyl piperazine (1) + water (2)} system at T = (298.15 to 343.15) K and atmospheric pressure

Densities (ρ) and viscosities (η) of aqueous 1-methylpiperazine (1-MPZ) solutions are reported at T = (298.15 to 343.15) K. Refractive indices (n_D) are reported at T = (293.15 to 333.15) K, and surface tensions (γ) are reported at T = (298.15 to 333.15) K. Derived excess properties, except excess viscosities (Δη), are found to be negative over the entire composition range. The addition of 1-MPZ reduces drastically the surface tension of water. The temperature dependence of surface tensions is explained in terms of surface entropy (S^S) and enthalpy (H^S). The measured and derived properties are used to probe the microscopic liquid structure of the bulk and surface of the aqueous amine solutions.     

Synthesis and Evaluation of Surface Activity of Gemini Borate Surfactants Based on Glucose Moiety

A series of Gemini borate surfactants were synthesized based on glucose molecule. Their chemical structures were confirmed using ¹H-NMR,¹³C nuclear magnetic resonance (NMR), and mass spectroscopy. The surface activities of these Gemini amphiphiles were measured, including surface tension (γ), critical micelle concentration (CMC), effectiveness (II_cmc), efficiency (pC₂₀), maximum surface excess (Γ_max), and minimum surface area (A_min) at different temperatures 25, 35, and 45°C either in pure water or in water–ethanol mixture (10%). Also, thermodynamic data including free energy, entropy, and enthalpy changes (ΔS, TΔS, ΔH) for adsorption at the air–water interface and also for micellization in surfactant solutions were calculated.     

A Nonpolar,Nonamphiphilic Molecule Can Accelerate Adsorption of Phospholipids and Lower Their Surface Tension at the Air/Water Interface

The adsorption dynamics of a series of phospholipids (PLs) at the interface between an aqueous solution or dispersion of the PL and a gas phase containing the nonpolar, nonamphiphilic linear perfluorocarbon perfluorohexane (PFH) was studied by bubble profile analysis tensiometry. The PLs investigated were dioctanoylphosphatidylcholine (DiC₈‐PC), dilaurylphosphatidylcholine, dimyristoylphosphatidylcholine, and dipalmitoylphosphatidylcholine. The gas phase consisted of air or air saturated with PFH. The perfluorocarbon gas was found to have an unexpected, strong effect on both the adsorption rate and the equilibrium interfacial tension (γ_eq) of the PLs. First, for all of the PLs, and at all concentrations investigated, the γ_eq values were significantly lower (by up to 10 mN m^?1) when PFH was present in the gas phase. The efficacy of PFH in decreasing γ_eq depends on the ability of PLs to form micelles or vesicles in water. For vesicles, it also depends on the gel or fluid state of the membranes. Second, the adsorption rates of all the PLs at the interface (as assessed by the time required for the initial interfacial tension to be reduced by 30 %) are significantly accelerated (by up to fivefold) by the presence of PFH for the lower PL concentrations. Both the surface‐tension reducing effect and the adsorption rate increasing effect establish that PFH has a strong interaction with the PL monolayer and acts as a cosurfactant at the interface, despite the absence of any amphiphilic character. Fitting the adsorption profiles of DiC₈‐PC at the PFH‐saturated air/aqueous solution interface with the modified Frumkin model indicated that the PFH molecule lay horizontally at the interface.     

Thermodynamic and spectroscopic studies on cationic surfactant tetradecyltrimethylammonium bromide in aqueous solution of trisubstituted ionic liquid 1, 2-dimethyl-3-octylimidazolium chloride at different temperatures

In this work, the effects on micellar behavior of long chain cationic surfactant tetradecyltrimethylammonium bromide (TTAB) upon the addition of trisubstituted ionic liquid (IL), 1, 2-dimethyl-3-octylimidazolium chloride [odmim][Cl] at temperatures, 298.15–318.15 K has been studied. Different techniques such as conductance, surface tension, fluorescence and ¹H NMR have been employed to understand the interactional mechanisms. The values of critical micelle concentration (cmc) and various thermodynamic parameters have been calculated from conductivity measurements. The surface parameters like effectiveness of decrease in surface tension (Π_cmc), minimum surface area occupied per surfactant monomer (A_min), maximum surface excess concentration (Γ_max), and adsorption efficiency (pC₂₀) have been evaluated by surface tension measurements. Micellar aggregation number (N_agg) has been determined by quenching of pyrene. Further to understand interactions in post micellar region, ¹H NMR measurements have been performed. It has been observed that the lipophilicity of interacting ion modified the thermodynamic and aggregation properties of TTAB.     

Novel Cationic Gemini Surfactants Based on Piperazine: Synthesis,Surface Activity,and Foam Ability

A series of novel Gemini surfactants C_n-pi-C_n with piperazine moiety as spacer was synthesized and characterized by IR, ¹H NMR, and mass spectra. Their surface activities were evaluated by surface tension, electrical conductivity, and steady-state fluorescence. The obtained results indicated that the synthesized Gemini surfactants exhibited lower critical micelle concentration (cmc) and surface tension (γ_cmc) compared with traditional surfactants. The steady-state fluorescence measurement and electrical conductivity were recorded to demonstrate the accuracy of cmc values. In addition, the micellization was evaluated using conductivity measurement in the temperature range of 298–308 K. The foamability and foam stability of these Gemini surfactants were also examined. In which, the Gemini surfactant with the shortest chain (C₁₂) showed the best foamability but the poorest foam stability. Hydrophile–lipophile balance and emulsifying ability were studied and a comparatively poor emulsifying ability displayed.     

Interfacial tension between polystyrene and a liquid crystal polymer

In this work contact angles formed by drops of polystyrene (PS) on a surface of liquid crystalline polymer (LCP) Vectra A910 were measured as a function of temperature for temperatures ranging from 180 to 230°C. The values were used together with the surface tensions of both polymers to evaluate the interfacial tension between PS and the LCP. In order to validate the method used to evaluate this interfacial tension, the interfacial tension between polypropylene (PP) and PS was evaluated using values of contact angles formed by a drop of PP on PS and the values of surface tension of both polymers in the molten state. The values of interfacial tension between PP and PS corroborated well the values obtained using the pendant drop method. The values of interfacial tension between PS and the LCP were shown to decrease linearly with temperature.     

Survismeter Unit for Surface Tension,Viscosity, and Dipole Moment Determination for Polystyrene Interactions in Benzene

Novel instrumental set up is developed for surface tension (γ, N m^?1), viscosity (η, N s m^?2)) and dipole moment (μ/Debye) measurements. A new instrument is economic, viable and pollution free in use, the γ, η and μ from viscosities (η, N s m^?2) and surface tension (γ, N m^?1) for 0.005 to 0.125 g% polystyrene at an interval of 0.0005 g% in benzene are measured at 288.15, 293.15, and 298.15 Kelvin temperatures. The γ, η, and μ are reported stronger frictional and cohesive forces due to stronger interactions of polystyrene with benzene. The survismeter is highly accurate and mechanically operated for pulling up liquid from reservoir bulb B1 to operational bulbs B2, B3, and B4. Densities are higher than those of benzene and also infer stronger polystyrene–benzene interactions, and hydrodynamic volume (HV) calculated with intrinsic viscosity [η] is noted in 293.15 (HV) >298.15 (HV) >288.15 (HV) order with higher values at 293.15 K. Surface tension (γ) values are slightly higher than of benzene and fall in a range of 33.47 to 33.35 N m^?1.     

The surface property and aggregation behavior of a hydrophobically modified cyclodextrin

The surface property of an amphiphilic cyclodextrin 2-O-(hydroxypropyl-N,N-dimethyl-N-dodecylammonio)-β-cyclodextrin (HPDMA-C₁₂-CD) was investigated using oscillating bubble rheometer and electrical conductivity method at different temperatures. The surface tension and dilational viscoelasticity of HPDMA-C₁₂-CD were provided. The results showed that HPDMA-C₁₂-CD could adsorb on the air–water interface, which decreased the surface tension of water efficiently. Critical micelle concentration (cmc) can be clearly defined from the surface tension isotherm. pC₂₀ and π _cmc were derived from the surface tension isotherms as well. The thermodynamic parameters (ΔG   ⁰ _m  , ΔH   ⁰ _m  , −TΔS   ⁰ _m) derived from electrical conductivity indicated that the micellization of HPDMA-C₁₂-CD was entropy-driven at lower temperature, while it was enthalpy-driven at higher temperature. The dilational modulus appeared a maximum value while the phase angle appeared two maxima as a function of HPDMA-C₁₂-CD concentration.     

Aggregation behavior and adsorption properties of salt-free catanionic surfactant mixtures containing tetradecyltrimethyl ammonium salts

The aggregation behavior of salt-free catanionic surfactants, tetradecyltrimethyl ammonium hydroxide (TTAOH)/fatty acid (FA) including octanoic acid (OA), decylic acid (DA) and lauric acid (LA) in aqueous solutions were studied. The critical micelle concentration(cmc), surface tension at cmc (γ_cmc), surface excess (Г_max), mean molecular surface area (A_min), adsorption efficiency (pc₂₀) and surface tension reduction effectiveness (π_cmc) were obtained from surface tension isotherms. The influence of temperature on the surface tension of salt-free TTAOH/FA (TTAOF) systems was investigated. Data of adsorption dynamics indicated that at fixed adsorption time, the order of adsorption capacity was TTAOH?相似文献   

Synthesis and properties of nonylphenol-substituted dodecyl sulfonate

Nonylphenol-substituted dodecyl sulfonate (C₁₂-NPAS) was synthesized via sulfonation-alkylation-neutralization using 1-dodecene, SO₃, and nonylphenol as raw materials. The properties such as surface tension, interfacial tension (IFT), wettability, foam properties, and salinity tolerance of C₁₂-NPAS were systematically investigated. The results show that the critical micelle concentration (CMC) of C₁₂-NPAS was 0.22?mmol?·?L^?1 and the surface tension at the CMC (γ_CMC) of C₁₂-NPAS was 29.4 mN/m. When compared with the traditional surfactants sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), and linear alkylbenzene sulfonate (LAS), the surface properties of C₁₂-NPAS were found to be superior. The IFT between Daqing crude oil and a weak-base alkaline/surfactant/polymer (ASP) oil flooding system containing 0.1?wt% of C₁₂-NPAS can reach an ultralow level of 2.79?×?10^?3 mN/m, which was lower than that found for the traditional surfactant heavy alkylbenzene sulfonate (HABS). The salinity and hardness tolerance of C₁₂-NPAS were much stronger than those found for conventional surfactants, petroleum sulfonate, and LAS. C₁₂-NPAS also shows improved wetting performance, foamability, and foam stability.     

Rate constants of the reactions of O(3P) atoms with Br2 and NO2 over the temperature range 220-950 K

The kinetics of the reactions of Br₂ and NO₂ with ground state oxygen atoms have been studied over a wide temperature range, T = 220-950 K, using a low-pressure flow tube reactor coupled with a quadrupole mass spectrometer: O + NO₂ → NO + O₂ (1) and O + Br₂ → Br + BrO (2). The rate constant of reaction (1) was determined under pseudo–first-order conditions, either monitoring the kinetics of O-atom or NO₂ consumption in excess of NO₂ or of the oxygen atoms, respectively: k₁ = (6.1 ± 0.4) × 10⁻¹² exp((155 ± 18)/T) cm³ molecule⁻¹ s⁻¹ (where the uncertainties represent precision at the 2σ level, the estimated total uncertainty on k₁ being 15% at all temperatures). The temperature dependence of k₁, found to be in excellent agreement with multiple previous low-temperature data, was extended to 950 K. The rate constant of reaction (2) determined under pseudo–first-order conditions, monitoring the kinetics of Br₂ consumption in excess of O-atoms, showed upward curvature at low and high temperatures of the study and was fitted with the following three-parameter expression: k₂ = 9.85 × 10⁻¹⁶ T^1.41 exp(543/T) cm³ molecule⁻¹ s⁻¹ at T = (220-950) K, which is recommended from the present study with an independent of temperature conservative uncertainty of 15% on k₂.     

CHARACTERIZATION OF γ-IRRADIATED CRYSTALLINE POLYMERS Ⅰ. CHARACTERIZATION OF γ-RADIATION INDUCED CROSSLINKED POLYAMIDE 1010 BY CRYSTALLIZATION TEMPERATURE*

The effect of ~(50)Co γ-radiation on plain polyamide 1010 (PA1010 Ⅰ) and PA1010 containing dif-ferent amount of crosslinking agent (BMI) (PA1010 Ⅱ) both in vacuum and in air at room tempera-ture was investigated with DSC. It was found that the crystallization temperature T_c of crosslinkedsample determined with DSC at constant cooling rate decreased as the radiation dose increased. Thedifference between crystallization temperatures before and after crosslinking (T_(c_o)-T_(c_R) is linearlyrelated to the radiation dose for PA1010I. Based on the Charlesby-Pinner's equation an expressionwas derived S+S~(1/2)=A+B/(T_(c_o)-T_(c_R)) where S is the sol fraction, A and B are constants. Since thereis evidence that T_c is relative to S only and independent of the way of irradiation, the equation is alsoapplicable to the enhanced γ-irradiation crosslinked PA1010 Ⅱ. Therefore, determination of T_cof crosslinked polymer by DSC offers a convenient approach to study quantitatively the random andespecially non-random crosslinking reaction of crystalline polymer.     

Silicon-Modified Carbohydrate Surfactants V: The Wetting Behaviour of Low-Molecular-Weight Siloxane,Carbosilane, Silane and Polysilane Precursors on Low-Energy Surfaces

The surface tensions, wetting tensions, contact angles and solid/liquid interfacial tensions of defined siloxanes as well as those of analogous carbosilanes, polysilanes and neopentyl substituted silanes were determined. The wetting experiments were carried out on a glass plate coated with perfluoroalkyl methacrylate (FC 722^®). The siloxanes possess the lowest surface tensions. Due to the presence of oxygen atoms in the siloxane backbone, a donor–acceptor portion (γ^+/−_lv) of the surface tension of about 1–2 mN/m was determined. The solid/liquid interfacial tension also contains a donor–acceptor portion (γ^+/−_sl). Its value is almost identical to that of γ^+/−_lv. The γ^+/−_sl differences between individual molecules of the same surface tension are responsible for contact angle differences of up to 4°. © 1997 John Wiley & Sons, Ltd.     

Comparative study of ionic interactions of 1 : 1 and 1 : 2 electrolytes of nitrates salts solutions with water analysed with physicochemical data

Densities (ρ), viscosities (η) and surface tension (γ) as function of the molarity of 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 for LiNO₃, NaNO₃, KNO₃, Sr(NO₃)₂, Ba(NO₃)₂ and Pb(NO₃)₂ electrolytes are reported at 32°C. Data were regressed for limiting values for solute–solvent interactions and effects of shell numbers and electronic configurations. A confidence variance of 95.5% at Gaussian distribution was noted. Densities explained ionic forces and sizes, and viscosities defined frictional forces while the surface tension focused surface energies of hydrated ions. Slopes of densities, viscosities and surface tensions explained the concentration effects on ionic interactions. Limiting densities from Li⁺ to Ba²⁺ increased with increase in sizes. Pb²⁺ smaller in size than the Ba²⁺ had lower limiting densities. The ρ ⁰ are Ba^2+?>?Sr^2+?>?Pb^2+?>?K^+?>?Na^+?>?Li⁺ with 3.24, 2.98, 4.53, 2.109, 2.257 and 2.38?×?10^3?kg?m^?3 densities of nitrate salts, respectively, in the solid state.