Dilute Solution Properties Research Articles

Thermodynamic properties of dilute solutions of selenium in liquid lead

The activity coefficients and activities of selenium in liquid alloys of the Pb-Se system at low selenium content were estimated from the available experimental data.

Hierarchical supramolecular structuring and dynamical properties of water soluble polyethylene glycol–perylene self-assemblies

The structural and dynamical properties of dilute aqueous solutions of poly(ethylene glycol)-perylene diimides (PEG(n)-PDI) have been investigated by means of static and dynamic light scattering, TEM microscopy, and small-angle X-ray scattering experiments. The amphiphilic PEG(n)-PDI molecules first self-assemble into stable and compact primary stacks of a few units of planar PDI through hydrophobic and π-π interactions. These primary stacks subsequently arrange in large and globular aggregates of typically 100-250 nm via weak PEG chain interpenetration. Surprisingly, the scattered electric field autocorrelation function g((1))(q,t) measured by dynamic light scattering evolves over very long periods of times (several months) and up to a bimodal distribution. The fast relaxation mechanism is associated to the diffusion of free primary stacks, whereas the slower relaxation still indicates the presence of large self-assemblies. Kinetic experiments show that the large supramolecular aggregates slowly release the free primary stacks whose proportion increases with time. This dissociation depends on several parameters such as PEG side chain length, total concentration, and shaking.

Flow Properties of Microbubble/Polyethylene Glycol Mixtures Passing through Orifices and Slits

Recently, a considerable amount of research has been conducted on microbubbles, and accordingly many papers have reported on the research results. For a microbubble/water mixture passed through a capillary tube to which lard oil had been applied, a mass removal rate of 0.3 was found, whereas a rate of 0.9 for only the microbubble/water mixture. Gotoh et al. separated oils in an emulsion by using microbubbles, and Tachibana reported on the medical application of a microbubble/liquid mixture as an ultrasonic contrast agent. Suzuki et al. showed that by suspending microbubbles in liquids, the turbulent structure was changed and the Reynolds stress was lowered. In addition, the drag coefficient was found to be reduced for microbubble/liquid mixtures in rectangular channels and capillary tubes by Murai et al. and Guin et al.. Thus, as seen above, a number of theoretical and applied studies have been previously conducted. However, only microbubble/water mixtures have been typically investigated. Studies on microbubble mixtures in complex liquids, for example, surfactant solutions and polymer solutions, are limited. In general, anomalous and interesting results have been reported from investigations on complex liquids. Okawara et al. measured the pressure drop in slit flows of a wormlike micelle surfactant and found that flow properties changed as the surfactant structure was changed. Ouchi et al. conducted an experiment using an aqueous solution of cetyltrimethylammonium bromide and sodium salicylate, which form wormlike micelles, and reported on the shear induced structure and instabilities. Ushida et al. examined the flow properties of several types of surfactants that form spherical micelles, and found a drag reduction in elongational flows. Hasegawa et al. measured the flow properties and the rheological properties of dilute aqueous solutions of polyethylene oxide. Furthermore, Ushida et al. investigated the pressure drops of surfactant/nanobubble mixtures. However, the study of nanoand micro-bubble/dilute polymer mixtures was rare case. In the present research, a dilute polymer solution in which microbubbles were suspended was passed through different sizes of orifices and slits. The Flow Properties of Microbubble/Polyethylene Glycol Mixtures Passing through Orifices and Slits

Dilute solution and rheological properties of hyperbranched polysaccharide from Pleurotus tuber-regium sclerotia

The dilute solution properties, critical coil overlap concentration, and rheological properties of the hyperbranched PTM3b polysaccharide were studied and compared. Flory factor (Φ) values of PTM3b in different solvents were smaller than those of linear chains as a result of the hyperbranched structure and wide polydispersity index. The relationships of ‘zero shear’ specific viscosity (ηsp,0) and coil overlap parameter (c[η]) were represented asηsp,0∝c1.05±0.03, ηsp,0∝c1.45±0.03 and ηsp,0∝c2.89±0.11 for the dilute, semi-dilute, and concentrated solution regions of PTM3b in 0.15 M aqueous NaCl, and coil overlap parameters were c*[η] = 0.07 and c**[η] = 0.29. Shear-thinning behavior was observed for PTM3b in 0.15 M aqueous NaCl in high concentration region, whereas Newtonian behavior in relatively low concentration region. The slope values of 2.34 and 12.8 were obtained from the double logarithmic plot of η0 versus c for PTM3b in 0.15 M aqueous NaCl. The slope value of 12.8 suggested that the hyperbranched polysaccharide resembled incompressible coils in the higher concentrated region. This work could provide some valuable and fundamental information to further understand the natural hyperbranched polysaccharide solutions from dilute to concentrated regions.

Dilute solution properties and degree of chain branching for dextran

Abstract Hydrodynamic volume, radius of gyration, and viscometric constants, K and a , for dextran, with a wide molecular weight range were calculated using experimental reported average-molecular weights ( M n , M w ), and intrinsic viscosity, [ η ], data in water and 0.05 M Na 2 SO 4 . Degree of chain branching for dextran was also determined using different procedures. This study demonstrated that hydrodynamic volume and radius of gyration of a dextran sample with M w M w are almost identical, whereas the latter parameters for a dextran sample with M w > 20 kDa was smaller than that of its linear counterpart. Values of 0.506 in water and 0.512, 0.425 and 0.273 in 0.05 M Na 2 SO 4 for the exponent a were obtained. A smaller value for a was obtained for a larger M w range. Molecular weights of desirable nano-particles for various branches of nanotechnology can be estimated from a derived radius of gyration–molecular weight relationship.

Critical Effects on Attractive Solutes in Binary Liquid Mixtures Close to Their Consolute Point: A New Experimental Strategy

The effect of near-criticality upon the properties of dilute solutions of attractive solutes has been previously studied only using pure solvents close to the vapor-liquid critical point. The experimental difficulties that plague this thermodynamic region have somewhat obscured the interpretations of the results. Consequently, the coupling of long-range critical fluctuations with short-range intermolecular interactions is still a matter of debate. We developed a new strategy consisting of studying the changes in the solvation shell of probe molecules dissolved in a binary solvent mixture close to its lower consolute critical point. The study is based on UV-vis absorption and fluorescent emission measurements of the solvatochromic and thermochromic effects of two dyes, Reichardt's Dye and Nile Red, dissolved in mixtures of lutidine-water. The results show unambiguously the existence of a subtle change in the composition of the near-critical solvent surrounding the probe molecules with respect to the bulk composition, thus we conclude that the coupling of long-range fluctuations with short-range interactions is now firmly established.

β-1,3-d-Glucan Schizophyllan/Poly(dA) Triple-Helical Complex in Dilute Solution

A certain length of poly(deoxyadenylic acid) (dA(X)) can form a novel complex with β-1,3-D-glucan schizophyllan (SPG) with a stoichiometric composition of one dA binding two main chain glucoses. We measured dilute solution properties for the complex with light and small-angle X-ray scattering as well as intrinsic viscosity and found that the complex behaves as a semiflexible rod without branching or cross-linking. We analyzed the data with the wormlike cylinder model, and the chain dimensions and the persistence length for the complexes were consistently determined. The chain flexibility was reduced to almost 25% upon complexation for dA/SPG and to 15% for S-dA/SPG, where S-dA denotes the phosphorothioated DNA analogue. The changes in the molar mass per unit length and the diameter indicated that the helix was elongated or stretched along the axis direction upon the complexation.

A study of the structure of lignin macromolecules

The hydrodynamic properties of dilute solutions of lignin isolated from mountain ash (Sorbus aucuparia) and apple (Malus domestica Borkh.) wood have been studied. The correlation between hydrodynamic and scaling characteristics of polymers has been considered. The results demonstrate that the topological structure of lignin macromolecules have a starlike shape with linear rays.

Structure and solution properties of cyanoethyl celluloses synthesized in LiOH/urea aqueous solution

Cyanoethyl celluloses (CECs) with different degree of substitution (DS) were synthesized by homogeneous reaction of cellulose (cotton linter pulp and absorbent cotton) with acrylonitrile (AN) in LiOH/urea aqueous solutions. The reaction showed quick reactivity and high transfer efficiency of etherification agent. The DS values of CECs were controlled by varying the molar ratio of AN to anhydroglucose unit (AGU) and the cellulose concentration. The DS values of the CEC-1–CEC-10 increased from 0.27 to 1.78 with increasing molar ratio of AN to AGU from 0.5:1 to 9:1. While the CEC-11–CEC-21 with DS values of 0.26–1.81 could be obtained by adjusting the molar ratio from 1:1 to 27:1. The relative reactivity of hydroxyl groups is in the order of C-6 > C-2 > C-3. The DS values of the water-soluble derivatives are in the range of 0.47–1.01. As the DS values increase to 1.37, CEC samples can not be dissolved in water or dilute alkali solution, but have good solubility in organic solvents, such as DMSO, DMF and pyridine. The dilute solution properties and molecular parameters of the CEC samples were studied by static light scattering and dynamic light scattering. The results indicated that the water-soluble samples could form a small number of aggregates spontaneously in 0.9 wt% NaCl aqueous solution, while the water-insoluble samples showed extended stiff chains in 0.5% LiCl–DMAc.

Photochromic azobenzene functionalised banana–calamitic dimers and trimers: mesophase behaviour and photo-orientational phenomena

Azobenzene functionalised banana–calamitic dimers and a novel type of banana–calamitic–banana trimers have been synthesised. Their thermotropic behaviour and the structure of the mesophases have been characterised by differential scanning calorimetry, polarising optical microscopy and X-ray diffractions measurements. Electro-optical studies evidence the polar properties of the smectic phases. A rare anticlinic–synclinic smectic CP (SmCP) phase transition could be proven for two of the twins upon cooling without an electric field although the molecules are not optically active. Remarkably, the phase sequence SmCa–SmCs has been observed upon cooling, the inverse sequence to that reported for non-chiral compounds up to now. A comparative study of the photochemical properties of dilute solutions and of thin films of two compounds has been performed. Irradiation with polarised ultra-violet (365 nm) and visible light (473 nm) induces a photo-orientation process of the chromophores in a direction perpendicular to the polarisation plane of the exciting light. For a trimeric compound bearing an azobenzene bridge between both bent-core mesogenic units this process is associated with cycles of the E–Z–E isomerisation of the azobenzene groups followed by rotational diffusion of molecules in the films. For a bis(azobenzene) containing dimer the E–Z isomerisation in films is strongly suppressed and the photo-induced orientation has a rotational diffusion mechanism.

Volumetric properties of dilute solutions of water in ethanol and water- d2 in ethanol- d1 between T = (278.15 and 318.15) K

Densities of solutions of H 2O in C 2H 5OH and D 2O in C 2H 5OD, with a water mole fraction ranging up to 0.037, were measured with an error of 1.0 · 10 −5 g · cm −3 at T = (278.15, 288.15, 298.15, 308.15, and 318.15) K and at atmospheric pressure using a precise sealed vibrating tube densimeter. Apparent molar volumes and isobaric expansibilities down to infinite dilution of a solute were calculated. The temperature-dependent behaviour of solute H/D isotope effects on the volumetric quantities studied was analysed taking account of structure-related peculiarities of the solvating media in question.

Aggregation behavior of amphiphilic random copolymer of 2-(acrylamido)-2-methylpropanesulfonic acid and tris(trimethylsiloxy)silylpropylmethacrylate in aqueous solution

Aggregation behavior including dilute solution property and surface-activity of the amphiphilic random copolymer composed of 2-(acrylamido)-2-methylpropanesulfonic acid and tris(trimethylsiloxy)silylpropylmethacrylate (AMPS/TRIS copolymer) in aqueous solution were studied by static light scattering (SLS), dynamic light scattering (DLS), surface tension measurement, and transmission electron microscopy (TEM). The surface tension measurement made it clear that AMPS/TRIS copolymer exhibited weaker surface-activity than a typical low-molecular weight surfactant sodium dodecyl sulfate in water, that is, there were no plateau of surface tension γ versus concentration and no critical micelle concentration (CMC) in the whole concentration studied. SLS and DLS analyses, and TEM revealed that AMPS/TRIS copolymer self-associated into imperfect core-shell micelles having hydrophobic TRIS core surrounded by hydrophilic AMPS shell in water. AMPS shell was considered as a hard shell due to the stiffness of AMPS chain in water. TRIS chain could not densely aggregate in water due to the large steric hindrance between bulky trimethylsiloxy groups despite its hydrophobic nature, thereby providing TRIS core with less-dense structure. The balance between the spreading force of stiff AMPS chain and the cohesion force of bulky TRIS chain provides the driving force for forming the unique micelle having less-dense TRIS core and hard AMPS shell. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

Effect of particle surface selectivity on composite nanostructures in nanoparticle/diblock copolymer mixture dilute solution

In this study the phase behavior of nanoparticle/diblock copolymer composites in dilute solution has been investigated by the hybrid particle-field (HPF) method. We focus on the influence of particle surface selectivity (i.e. hydrophobic and hydrophilic) on the distribution of nanoparticles in the micelles formed by the diblock copolymers. These two types of particle surface selectivity are simulated systematically. The different competition between the energy from enthalpy and the energy from entropy has been observed in the two kinds of composite systems. Our simulation results show that the particle surface selectivity is a crucial factor for determining the thermodynamic properties in the complex dilute solution, and the morphologies of micelles are controlled by the volume fraction of the nanoparticles. The change of particle distribution in various micelles enriches the composite microstructures that can be formed by nanoparticle and diblock copolymer.

Elastic instability in stratified core annular flow

We study experimentally the interfacial instability between a layer of dilute polymer solution and water flowing in a thin capillary. The use of microfluidic devices allows us to observe and quantify in great detail the features of the flow. At low velocities, the flow takes the form of a straight jet, while at high velocities, steady or advected wavy jets are produced. We demonstrate that the transition between these flow regimes is purely elastic--it is caused by the viscoelasticity of the polymer solution only. The linear stability analysis of the flow in the short-wave approximation supplemented with a kinematic criterion captures quantitatively the flow diagram. Surprisingly, unstable flows are observed for strong velocities, whereas convected flows are observed for low velocities. We demonstrate that this instability can be used to measure the rheological properties of dilute polymer solutions that are difficult to assess otherwise.

An upper limit for macromolecular crowding effects

BackgroundSolutions containing high macromolecule concentrations are predicted to affect a number of protein properties compared to those properties in dilute solution. In cells, these macromolecular crowders have a large range of sizes and can occupy 30% or more of the available volume. We chose to study the stability and ps-ns internal dynamics of a globular protein whose radius is ~2 nm when crowded by a synthetic microgel composed of poly(N-isopropylacrylamide-co-acrylic acid) with particle radii of ~300 nm.ResultsOur studies revealed no change in protein rotational or ps-ns backbone dynamics and only mild (~0.5 kcal/mol at 37°C, pH 5.4) stabilization at a volume occupancy of 70%, which approaches the occupancy of closely packing spheres. The lack of change in rotational dynamics indicates the absence of strong crowder-protein interactions.ConclusionsOur observations are explained by the large size discrepancy between the protein and crowders and by the internal structure of the microgels, which provide interstitial spaces and internal pores where the protein can exist in a dilute solution-like environment. In summary, microgels that interact weakly with proteins do not strongly influence protein dynamics or stability because these large microgels constitute an upper size limit on crowding effects.

Aggregation and surface properties of synthetic double-chain non-ionic surfactants in aqueous solution.

Double-chain non-ionic surfactants have been synthesized with the general formula 2CnMPEG750, where n is the number of carbons in the alkyl chains and 750 is the molecular weight of the monomethoxypolyoxyethylene (MPEG) head group. The aggregation and surface properties in dilute aqueous solution (< 1.0% w/w) of surfactants with n = 8, 10 and 12 have been determined. Each of the surfactants formed clear, foaming, non-birefringent solutions. Total-intensity light scattering indicated the presence of micelles with aggregation numbers of 36, 68 and 74 for the 2C8, 2C10 and 2C12 surfactants, respectively, whereas photon-correlation studies yielded radii, assuming spherical aggregates, of 59-103 A. Surface-tension measurements gave critical micelle concentrations for the surfactants in the range 1.15-7.24 x 10(-6) M; these, as expected, decreased when the number of carbon atoms in the alkyl chains was increased. Such studies are important in the design of new surfactants as vehicles for drug delivery because it is imperative to be able to predict the type of aggregate formed by a surfactant.

Dilute solution properties of clindamycin 2-palmitate hydrochloride.

Clindamycin 2-palmitate hydrochloride forms micelles in aqueous solution at concentrations above 2-2 X 10(-3) M. Dilution of micellar solutions of the drug to concentrations less than 2-0 X 10(-3) M produces turbid systems. Turbidity is caused by unionized drug, produced by hydrolysis of the salt, phasing out of solution at concentrations too low for micelles to be formed. Changes in specific conductivity and turbidity associated with the phasing-out process have been measured and explained in terms of the rates of the various processes involved, including demicellization and emulsion stability. The phenomenon of phasing-out, below a critical concentration in aqueous solution, is predicted to be a general one for weakly ionized surfactants where the unionized species possesses low water solubility.

Micellization and Micellar Aggregation of Poly(ethylene-alt-propylene)-b-poly(ethylene oxide)-b-poly(N-isopropylacrylamide) Triblock Terpolymers in Water

Three poly(ethylene-alt-propylene)-b-poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PEP−PEO−PNIPAm, “PON”) triblock terpolymers were synthesized using a combination of anionic and reversible addition−fragmentation chain transfer polymerization, and their micellization and micellar aggregation properties in dilute aqueous solution were studied by dynamic light scattering (DLS) and cryo-TEM. The PEP and PEO blocks had molecular weights of 3000 and 25 000, respectively, while the PNIPAm block was varied with molecular weights equal to 4000, 10 000, and 21 000. In dilute aqueous solution the terpolymers formed well-defined micelles with hydrophobic PEP cores surrounded by hydrophilic PEO−PNIPAm coronas at temperatures below the lower critical solution temperature (LCST) of PNIPAm. DLS revealed that the PON micelles prepared by a dialysis technique were significantly smaller than those prepared by a thin-film hydration technique. In either case, at temperatures above the LCST of PNIPAm, the micelles assoc...

묽은 용액의 성질에 대한 화학전공 예비교사들의 이해 및 화학교사 양성교육에 대한 인식 사례 연구

ABSTRACT. We compared the understanding of 4 pre-service teachers of chemistry education major and 2 pre-service teachersof chemistry major related to conceptions of of dilute solutions chapter in high school Chemistry II textbooks. As re-sults, few pre-service teachers understood fully the concepts of high school Chemistry II textbooks. Some pre-service teachers hadmisconceptions related to properties of dilute solutions. We fou nd that few differences existed between the pre-service teacher s' understanding regardless of whether they took a major in chemistry education of a education college or a major in chemistry of non-education college. Most of the pre-service teachers who attended this research recognized the lack of practical knowledge in th eirpre-service teacher curriculum. Keywords: Pre-service teacher, ChemistryII textbook, Teacher education curriculum, Property of dilute solution, Pedagogicalcontent knowledge 묽은 용액의 성질에 대한 화학전공 예비교사들의 이해 및 화학교사 양성교육에 대한 인식 사례 연구

Synthesis of Star Hydrophobically Modified Acrylamide Copolymer and its Dilute Solution Behavior in Water

The primary objective of this work was to prepare star copolymers of acrylamide and N,N-dimethyl-N-vinylnonadecan-1-aminium chloride(C18DMAAC) and to investigate the dilute solution behavior of these star hydrophobically modified acrylamide (SHMPAM) copolymers with different C18DMAAC content. The SHMPAMs were prepared using photopolymerization. For the different polymer solutions, the relationship between specific viscosity and polymer concentration obeyed the Rabin's relation well, which means that the conformations of these polymer chains were nearly spherical in dilute solution. The data of these dilute solutions were fitted by four different equations. The results showed that Schulz–Blaschke(S–B) and Fedors equations more accuratly described the dilute solution properties of these kinds of copolymers. The intrinsic viscosities calculated by different equations were different from each other, which is different from the results found for linear HMPAM. The equivalent hydrodynamic volume (voluminosity VE ) of these star copolymer solutions can not calculated by the regular method because the relationship between Y (Y = (ηr 0.5−1)/C (1.35ηr 0.5−0.1), ηr is relative viscosity and C is polymer concentration) and polymer concentration was abnormal.