Hildebrand Theory Research Articles

Synergistic effects of an amphiphilic drug(propranolol hydrochloride) with cationic surfactants in an aqueous medium: A physicochemical study

The interactions of amphiphilic drug(propranolol hydrochloride, PPL) with cationic surfactants, such as dodecyltrimethylammoniumbromide(DTAB), tetradecyltrimethylammonium bromide (TTAB), trimethyltetradecylammonium chloride(TTAC) and tetyltrimethylammonium bromide(CTAB), in an aqueous medium were evaluated. The surface tension measurement was used to examine the mixed micellization behavior and surface properties of drug-surfactant mixtures. The nonideal or synergistic behaviors of the mixed systems were explored by using several physical models, such as Clint, Rubingh, Rosen, and Motomura models, based on regular solution theory and pseudophase approximation. In addition, the synergism between PPL and cationic surfactants was also confirmed using ultraviolet–visible spectroscopy. The stoichiometric ratios, binding constants, and free energy changes of the drug–surfactant mixtures were computed using Benesi–Hildebrand (B–H) theory.

Some factors affecting pore size in the synthesis of rigid polymer monoliths: Theory and its applicability

AbstractMacroporous monoliths represent now widely used materials whose successful application strongly depends on their characteristics. Among those the average pore size is one of the key parameters. In this paper, we consider the applicability of theoretical calculations for the selection of appropriate porogens to generate the materials with required average pore size. A set of macroporous poly(meth)acrylate monoliths was synthesized via thermo‐ and photo‐initiated free radical polymerization and characterized in regards to their average pore size. Additionally, the difference in solubility parameters as well as Hansen's solubility parameter distance between monomers and porogens were calculated for each polymerization mixture using Hildebrand's and Hansen's solubility theories. The theoretical predications and experimental data were compared and analyzed to establish the applicability of theoretical calculations to previse average pore size for different systems. It was found that Hildebrand's theory seems to be poorly appropriate as universal tool, while Hansen's theoretical approach explained better the efficiency of solvents as porogens. The application of oligomers and polymer solutions due to the increase of viscosity as well as the variation of crosslinker amount in the monomer system can be singled out as Hansen's theory limitations at the prediction of the average pore size.

Study on the polarity and molar surface Gibbs energy of ether-based amino acid ionic liquids [COC4mim][Gly], [COC4mim][Ala] and [COC4mim][Thr

Ether-based functionalized amino acid ionic liquids have the advantages of its unique Contribution to low viscosity and high conductivity, as well as the biodegradability of amino acids. Three kinds of ether-based functionalized amino acid ionic liquids 1-(4-methoxybutyl)-3-methylimidazolium glycine ([COC4mim][Gly]), 1-(4-methoxybutyl)-3-methylimidazolium alanine ([COC4mim][Ala]) and 1-(4-methoxybutyl)-3-methylimidazolium threonine ([COC4mim][Thr]) were synthesized. And physicochemical properties, including density, surface tension and refraction, were measured at different experimental conditions. Based on the polarity scale of ionic liquids proposed by Hildebrand theory, an equation of the polarity coefficient Py was proposed. And we found that it can be applied into the determination of polarity for both ionic liquids and molecular liquids. The surface tension of [COC4mim][Gly], [COC4mim][Ala] and [COC4mim][Thr] was estimated by the definitions of the molar surface Gibbs energy and molar refraction. The predicted values γ(pre) have a very high linear correlation with the corresponding experimental ones.

Interaction of Diphenhydramine Hydrochloride with Cationic and Anionic Surfactants: Mixed Micellization and Binding Studies

The focus of the present work is to evaluate the interactions of an anti-allergic drug (diphenhydramine hydrochloride, DPH) with anionic (sodium dodecyl sulfate, SDS) and cationic (cetylpyridinium chloride, CPC) surfactants in the aqueous medium. The mixed micellization behavior and surface properties of drug-surfactant mixtures have been examined by surface tension measurements. Various theoretical approaches were applied to explore the synergistic or non-ideal behavior of the current mixed systems. Furthermore, the binding studies of drug with surfactants have been elaborated by UV–visible spectroscopy. Benesi–Hildebrand (B-H) theory was used to compute stoichiometric ratio, binding constant, and free energy change for the drug-surfactant mixtures. The outputs are deliberated taking into consideration the use of surfactants as capable drug delivery agents for DPH and hence advance bioavailability.

Immobilized enzyme reactors based on monoliths: Effect of pore size and enzyme loading on biocatalytic process.

Macroporous monolithic columns with different mean pore size (from 360 to 2020nm) and appropriate flow-through properties were synthesized using free radical in situ copolymerization of glycidyl methacrylate, 2-hydroxyethyl methacrylate and ethylene dimethacrylate. In order to predict the composition of porogen mixture to generate the pores in the interested size interval, the Hildebrand theory was used. Ribonuclease A and its specific low- and macromolecular substrates cytidine-2',3'-cyclic monophosphate sodium salt and RNA were applied as model system. The effect of mean pore size of macroporous monoliths used for enzyme immobilization on molecular recognition and biocatalytic characteristics was examined. The monitoring of RNA degradation was performed using anion-exchange HPLC on monolithic CIM DEAE analytical column. The high efficiency of heterogeneous biocatalysts obtained comparatively to the catalytic reaction of RNA degradation in solution was demonstrated. Additionally, the series of six monolithic immobilized enzyme reactors with different amount of biocatalyst was prepared and studied regarding to the biocatalytic properties at recirculation mode at two experimental variants, e.g. (i) fixed range of concentrations of circulated substrate solutions, and (ii) fixed range of substrate/enzyme molar ratios.

Effect of TiO2 nanoparticles on newly synthesized phenothiazine derivative-CPTA dye and its applications as dye sensitized solar cell

In this paper, effect of titanium dioxide (TiO2) nanoparticles (NPs) on newly synthesized phenothiazine dye i.e., (Z)-2-cyano-3-(10-heptyl-10H-phenothiazin-7-yl) acrylic acid (CPTA dye) has been studied using spectroscopic techniques such as absorption, fluorescence and electrochemical. Absorption spectra of CPTA dye in the presence of TiO2 appears broadened without any shift in the absorption peaks which suggests possible interactions between the CPTA dye and TiO2 NPs and absence of complex formation. These inferences were validated by determining association constant (ka) according to Benesi–Hildebrand theory. In order to see the role of fluorescence quenching, S-V theory was invoked, it was observed that phenomenon of quenching follows dynamic or collisional process under both steady and transient states. Experimentally determined magnitude of bimolecular quenching rate parameter is equal to the order of maximum collisional quenching rate parameter. Role of energy transfer between CPTA dye and TiO2 NPs has been discussed using Rehm-Weller theory. From this it reveals that electron transfer process is more pronounced under more polar solvent (Methanol) than less polar solvent (ethyl acetate). Electron transfer mechanism has been exploited in solar energy harvesting applications by fabricating solar cell sensitized by CPTA dye. From this, it was observed that the efficiency and fill factor of fabricated DSSC was 2.15% and 0.58 respectively under optimized conditions and solar harvesting property of newly synthesized phenothiazine derivative of CPTA dye is the first report.

픽처레스크 정원에 나타난 촉지적 지각 - 18세기 영국 픽처레스크 정원을 중심으로 -

시각중심주의에 편향된 근대의 광학적 메커니즘은 시각의 다채로운 기능을 간과하고 추상적이며, 이성적인 눈으로 사물을 판단하고 공간을 조직함으로써 눈이 사물을 더듬는 기능에 대해서는 간과하였다. 최근에는 시각의 이분법적 지각체계를 넘어서 복합지각에 의해 다른 감각과의 소통을 통한 다양한 경험을 유도하고 있다. 촉지적 지각은 시각뿐만 아니라 다양한 감각과의 상호작용을 통해 주체로 하여금 신체를 동반한 체험을 유도하며, 물성이 가지고 있는 특질과 인간의 다양한 감각적 자극을 꾀하는 역동적인 시각이다. 본 논문은 주체의 능동적 체험을 유도하는 촉지적 지각의 이론적 배경을 고찰하여 촉지적 지각의 주요한 특징을 도출하고 촉지적 지각의 특징이 픽처레스크 정원에서 어떠한 방식으로 나타나는지를 살펴보고자 한다. 촉지적 지각의 주요한 특징을 고찰하기 위해 철학과 미학사에서 아돌프 힐데브란트의 시각론이 알로이스 리글과 빌헬름 보링거, 발터 벤야민, 모르스 메를로 퐁티, 질 들뢰즈에 의해 각각 어떻게 발전, 확장, 재해석되는지를 탐구한다. 이로서 촉지적 지각과 시각적 지각 방식의 주요차이점을 분석하고 촉지적 지각이 가지는 특성을 도출한다. 이후, 촉지적 지각의 특성이 픽처레스크 정원에 어떻게 나타나는지 고찰하기 위해 고전적 정원을 시각적 지각으로 픽처레스크 정원을 촉지적 지각으로 각각 설정하여 분석하고 앞서 도출된 촉지적 지각의 특성을 픽처레스크 정원에 투영하여 고찰한다. 본 연구를 통해 도출된 픽처레스크 정원에 나타난 촉지적 지각에 대한 연구결과는 다음과 같다. 시각적 지각과 대별되는 촉지적 지각의 주요차이점은 경계의 모호함과 애매함, 동적시점의 생성, 불확정적 동선에 의한 운동성 유발, 지각 불가능성에 의한 낯설음과 숭고미로 요약할 수 있다. 픽처레스크 정원에서 경계의 모호함과 애매함은 평면의 불규칙함과 비대칭 요소, 단일시점의 거부로 나타나며, 동적시점의 생성은 서사적 구조의 도입과 회화의 장면구성기법을 재현하면서 기존 정원에 없는 전경, 중경, 원경 요소를 만들면서 공간을 중첩시킴으로써 생성된다. 불확정적 동선에 의한 운동성 유발은 분기하는 동선에 의해 형성되며, 지각 불가능성에 의한 낯설음과 숭고미는 정원에서 다양한 요소의 활용과 '거칠음'과 '불규칙함', '폐허'의 도입으로 나타난다. Modern optical mechanisms slanted toward Ocular-centrism have neglected diverse functions of vision, judged objects in abstract and binary perspectives, and organized spaces accordingly, there by neglecting the function of eyes groping objects. Recently, various experiences have been induced through communication with other senses by the complex perception beyond the binary perception system of vision. Haptic perception is dynamic vision that induces accompanying bodily experiences through interaction among the various senses; it recognizes the characteristics of material properties and various sensitive stimulations of human beings. This study elaborates on the major features of haptic perception by examining the theoretical background of this concept, which stimulates the active experience of the subject and determines how characteristics of haptic perception are displayed in picturesque gardens. In order to identify the major features of haptic perception, this study examines how Adolf Hildebrand's theory of vision is developed, expanded, and reinterpreted by Alois Riegl, Wilhelm Worringer, Walter Benjamin, Maurice Merleau Ponty, and Gilles Deleuze in the histories of philosophy and aesthetics. Based thereon, the core differences in haptic perception models and visual perception models are analyzed, and the features of haptic perception are identified. Then, classical gardens are set for visual perception and picturesque gardens are set for haptic perception so that the features from haptic perception identified previously are projected onto the picturesque gardens. The research results drawn from this study regarding features of haptic perception presented in picturesque gardens are as follows. The core differences of haptic perception in contrast to visual perception can be summarized as ambiguity and obscureness of boundaries, generation of dynamic perspectives, induction of motility by indefinite circulation, and strangeness and sublime beauty by the impossibility of perception. In picturesque gardens, the ambiguity and obscureness of boundaries are presented in the irregularity and asymmetric elements of planes and the rejection of a single view, and the generation of dynamic perspectives results from the adoption of narrative structure and overlapping of spaces through the creation of complete views, medium range views, and distant views, which the existing gardens lack. Thus, the scene composition technique is reproduced. The induction of motility by indefinite circulation is created by branching circulation, and strangeness and sublime beauty are presented through the use of various elements and the adoption of 'roughness', 'irregularity', and 'ruins' in the gardens.

Hydrogen solubility in heavy oil systems: Experiments and modeling

Hydrogen solubility measurements in heavy oils are required in order to develop accurate process models. Nevertheless, these solubility measurements are challenging at elevated temperatures and pressures and the amount of data points is scarce in the literature. This paper presents measured hydrogen solubilities in heavy oil systems at a temperature range from 498 to 598K and a pressure range from 2 to 11MPa. The experiments were conducted with a continuous flow apparatus. One of the well-characterized heavy oil systems was a hydrocracked vacuum gas oil and the second system consisted of a modified vacuum residue from Urals crude and toluene. The modified vacuum residue and toluene mixtures were prepared gravimetrically (mass fractions of vacuum residue: 0.25, 0.34 and 0.50). The experiments demonstrated that increasing the partial pressure of hydrogen and temperature increased the hydrogen solubility. Another finding was that the amount of toluene in the system had great impact to the hydrogen solubility. Four modeling approaches were compared based on their predictions on the hydrogen solubility in heavy oil systems measured in this work and four heavy oils found from the literature. The chosen models were PC-SAFT, Peng–Robinson, a simple correlation based on the corresponding theory and a method based on the Scatchard–Hildebrand theory. PC-SAFT with applied a heavy oil characterization method and the correlation based on the corresponding theory were found to predict the hydrogen solubility equally well and accurately. The benefit of using PC-SAFT instead of the simple correlation is that with PC-SAFT, phase behavior of multicomponent systems can be predicted and other properties, such as densities, can be obtained simultaneously. Peng–Robinson with a single carbon number characterization method overestimated the hydrogen solubility in the studied heavy oils and the method based on the Scatchard–Hildebrand theory could model the hydrogen solubility well after parameter regression.

Acoustical and spectroscopic investigation of charge transfer complexes of certain aromatic compounds with iodine in n-hexane at 303 K

Charge transfer complexes formed between iodine (acceptor) and six aromatic compounds, namely, benzene, pyrrole, thiophene, pyridine, quinoline and 2-methylquinoline (quinaldine) in n-hexane medium have been investigated by ultrasonic and UV–visible spectroscopic techniques at 303K. The measured values of ultrasonic velocity, density and viscosity were used to compute acoustical parameters and excess thermodynamic parameters. The trend in acoustical parameters with concentration identifies the existence of strong interactions amongst the solutes and the sign and magnitude of excess parameters establish the possibility of complex formation between the solute molecules. The specific interaction between the solutes is identified through the UV–visible spectra using Benesi–Hildebrand theory. The formation constants (K) of the charge-transfer complexes were determined by the Benesi–Hildebrand equation (spectroscopic method) and compared with those obtained by Kannappan method (ultrasonic). The trend in K values obtained by ultrasonic and spectral methods is similar and is explained with the structures of the donor molecules.

Spectroscopic and ultrasonic studies on the hydrogen bonded complexes of aromatic aldehydes with phenol in hexane medium

The molecular interactions have been studied in the ternary systems of phenol with three structurally different aromatic aldehydes, viz., benzaldehyde, cinnamaldehyde and salicylaldehyde in n-hexane medium, through the behavior of measured ultrasonic velocity ‘u’, density ‘ρ’, dynamic viscosity ‘η’ and the calculated acoustic parameters at 303.15K and at atmospheric pressure. Excess thermo acoustic parameters reveal the existence of hydrogen bonded complexes between aldehydes and phenol. The variation of the excess parameters both in sign and magnitude within the range of concentration investigated is also discussed in terms of structural aspect and functional groups of the components involved. The existence of solute interactions is also confirmed through electronic absorption spectra with Benesi–Hildebrand theory at 303.15K. The formation constants of the donor and acceptor complexes determined both by spectroscopic and ultrasonic methods are comparable and follow similar trend. The trend in the formation constants is discussed based on structures of the component molecules in terms of field effects.

Thermodynamic properties of donor–acceptor complexes of tertiary amine with aryl ketones in hexane medium

The thermodynamic stability of complexes formed between N,N-dimethylaniline (DMANI) and three ketones, namely, acetophenone (ACP), 4-chloroactophenone (ClACP) and 4-methylacetophenone (MACP) in n-hexane is extensively investigated by spectral and ultrasonic methods. The ultrasound scan was carried out in the temperature range 208.15–313.15 K and at atmospheric pressure on solutions containing equimolar concentrations of components ranging from 0.025 to 0.2 M. The existence of solute–solute interactions has also been confirmed through electronic absorption spectra analyzed with Benesi - Hildebrand theory at 303.15 K. The stability constants of the donor–acceptor complexes determined both by spectroscopic and ultrasonic methods are comparable and follow similar trends. The trend in the formation constants is discussed with structures of the components. The thermodynamic behavior of the systems was explained through the computed values of the free energy (Δ G ), enthalpy (Δ H ) and entropy (Δ S ) changes for complex formation are computed and discussed.

Swelling of medical grade silicones in liquids and calculation of their cross-link densities

Four medical grade silicones were swollen, until they reached equilibrium (i.e. constant mass) in eight liquids at 25 °C. The greatest swelling was obtained with n-heptane but the volume fraction, ϕ, of the silicones in their swollen state was not significantly different ( p < 0.05) in this liquid than in cyclohexane. For each grade of silicone, ϕ was plotted against δ l , the liquid solubility parameter, for each liquid in which it was swollen. A second-order polynomial was plotted through the results; the minimum in this polynomial provided a value for the polymer solubility parameter, δ p . The Flory polymer–liquid interaction parameter, χ, was calculated for the four best liquids, using Hildebrand's solubility parameter theory. An alternative method for calculating χ, directly from swelling measurements, was shown to produce physically unreasonable results. The cross-link density, υ, was calculated, from ϕ and χ, for each grade of silicone, using the Flory–Rehner equation. Since the values of two parameters involved in Hildebrand's theory cannot be determined reliably and because the Flory–Rehner equation is an approximation, absolute values of υ cannot be obtained. However, the relative values of υ obtained were higher for the harder grades then for the softer grades and similarly, the grades with the higher Young's modulus had higher υ values.

Structural transition of a homopolymer in solvents mixture

The present work is aimed at studying the thermodynamic behaviour of a polymer in solvents mixture. Dynamic light scattering is used to measure the hydrodynamic radius of polyvinylpyrrolidone ( M w = 360,000 g/mol), in water/methanol solvents mixture, versus the mixed solvents composition at 25 °C. Then, we show that the polymer conformation adopts the Coil–Globule–Coil structure when the methanol molar fraction X A is varied. This transition is attributed to solvent quality change which result from water and methanol complex formation. The polymer contraction rate calculated for each composition takes its maximum value at X A = 0.17. Hildebrand theory assuming the solvents mixture as an equivalent solvent was used to analyze the change in mixed solvents quality. These changes can be attributed to dispersive forces in solvents mixture.

Asphaltenes Flocculation in Light Crude Oils: A Chemical Approach to the Problem

This article describes the state‐of‐the‐art of the phenomena associated to the flocculation and precipitation of asphaltenes as well as the solutions used to prevent this kind of phase behavior problem in a Brazilian light (420 API) crude oil. A discussion on how to diagnose this light crude tendency to flocculate its low concentration (0.3%) asphaltenes and on the approach to (chemically) mitigate the phenomena also are provided. To address the problem a comprehensive study was carried out as follows: 1) Scoping trials to assess the so‐called asphaltenes deposition envelope (ADE) of the crude, a key parameter to design the chemical injection system and to production management. To accomplish that a mono‐phase crude oil sample was collected and tests were performed on a PVT cell equipped with a solid detection system. These PVT results enabled us to evidence the reversibility of the asphaltenes flocculation process—above the bubble point pressure—which is in agreement with the Hildebrand theory for macromolecules in hydrotopic solutions and; 2) A suite of field experiments to address the following issues: asphaltenes flocculation inhibitor dosage optimization; how to collect inhibitor‐free oil samples for well site evaluation; adaptation of the existing analytical methods for well site analysis and: setting up guidelines against which measure the inhibitor performance in this low‐asphaltenes concentration crude oil. The engineered solutions that ended up being developed from this comprehensive study are now incorporated to Petrobras flow assurance solutions portfolio.

A Fluorescence Spectroscopy Study of Preferential Solvation in Binary Solvents

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A fluorescence spectroscopy study of preferential solvation in binary solvents

Published data are reviewed on the dynamics of nonspecific preferential solvation in binary solvents, as obtained by fluorescence spectroscopy (in particular, by magnetic spin fluorescence method) using probe molecules in which strong charge redistribution yielding dipoles and ion pairs takes place upon excitation. The dynamics of preferential solvation of the excited probe in a binary solvent is described by a sequence of consecutive equilibrium reactions, in which each step is the absorption of a molecule of the polar component by the solvation shell of the excited probe, where transport from the bulk solution occurs via translational diffusion. The characteristic effect of the time saturation of solvation is attributed to the energetically unfavorable process of interface formation between the solvation shell, which a polar nanosized cluster, and the homogeneous binary mixture. Such polar clusters may affect the course of photochemical reactions involving charged species or particles with a large dipole moment. Simple model concepts, such as the Frenkel theory of heterophase fluctuations, the Onsager model, and the Hildebrand theory of solubility used for the description of the physical picture of preferential solvation, are considered.

Method to Calculate the Solubilities of Light Gases in Petroleum and Coal Liquid Fractions on the Basis of Their P/N/A Composition

In this paper, a paraffinic/naphthenic/aromatic (P/N/A) compositional model is proposed for calculation of the solubilities of light gases such as methane, ethane, carbon dioxide, and hydrogen in various petroleum and coal liquid fractions under different conditions of temperature and pressure. The proposed model uses Scatchard−Hildebrand theory with a corrected value for the solubility parameter of the dissolving gas and characterizes the liquid phase by its P/N/A composition. The results show that, for the fractions studied, the P/N/A composition has an effect on gas solubility. The model correlated the solubilities of gases with an average error of 4.5% when evaluated with 11 fractions and more than 180 data points for a pressure range of 5−250 bar. Corrected solubility parameters for hydrocarbon gases are recommended for their use with petroleum fractions and coal liquids of different P/N/A compositions. The main advantage of the proposed approach is that no experimental data are required to adjust any binary parameter. The approach is of direct use with the values of the solubility parameters reported in this work and characterization parameters of the fraction.

The coexistence curves and amplitude scaling of critical solutions of cycloalkane in N-methyl-2-pyrrolidone

Abstract The power-law dependences of critical amplitudes either on the molar volume of cycloalkane or on the interaction parameter per unit volume for coexistence curve, correlation length and susceptibility have been derived from a Landau–Ginsburg–Wilson model and the Scatchard–Hildebrand theory for solutions of cycloalkanes in a polar solvent. Coexistence curves of ( T , n ), ( T , x ) and ( T , ϕ ), where n , x , and ϕ are refractive index, mole fraction and volume fraction respectively, for the binary mixtures of methylcyclopentane and cycloheptane in N -methyl-2-pyrrolidone (NMP) have been determined in the critical regions by measurements of n . The critical amplitude B and the critical exponent β have been deduced. The experimental results reported in this work and previous work are in good agreement with theoretical predictions.

Solubility of carbon dioxide in alkylcarbonates and lactones

The solubility of carbon dioxide in γ-butyrolactone (BL), caprolactone (CL), propylene carbonate (PC), ethylene carbonate (EC), dimethylcarbonate (DMC), diethylcarbonate (DEC), and mixtures of these components has been determined at temperatures from 275 to 333 K at atmospheric pressure. The Henry's law constant (kH) for the dissolution of CO2 in these solvents has been deduced from the solubility data. The value of kH increases in the following order: DEC &lt; DMC &lt; PC &lt; CL &lt; BL &lt; EC, which is identical to the order of the Hildebrand parameters (δ) of the corresponding solvents. The accuracy of classical theories for predicting gas solubilities in liquids has been examined. The best results are given by the Vilcu–Perisamu equation, which is derived from the Scatchard–Hildebrand theory but takes into account the polarizability of the solute and the permittivity of the solvent. A modified form of the Prausnitz and Shair equation is proposed to estimate the solubility of nonpolar molecules in strongly dipolar solvents. This equation fits the experimental data with improved precision.Key words: alkylcarbonate, lactone, carbon dioxide, liquid–gas equilibrium, Henry's law, Hildebrand parameter.

Plano em repouso / plano em tensão: considerações sobre a teoria da forma de Adolf von Hildebrand e a arte brasileira do século XX

The text wants to think about the links and opositions between the Adolf von Hildebrand's Theory of Form and the Brazilian art of this century.