Self-consistent field theory investigation of the behavior of hyaluronic acid chains in aqueous salt solutions

In this work we continue to develop a field-theoretic methodology, which combines the technique of Gaussian equivalent representation for the calculation of functional integrals with the continuous Gaussian thread model of flexible polymers for solving statistical–mechanical problems of polyelectrolyte solutions. We present new analytic expressions for the osmotic pressure, the potential of mean force, and the monomer–monomer pair distribution function, and employ them to investigate the structural and thermodynamic quantities of the polyelectrolyte system. We demonstrate the applicability of the method for systems of polyelectrolyte chains in which the monomers interact via a Yukawa-type pair potential. As a specific example, the present work focuses on aqueous solutions of hyaluronic acid with added salts NaCl and CaCl₂. Hyaluronic acid is a high molecular weight linear polysaccharide, which has a multitude of roles in biological tissues. We conclude that the effect of sodium chloride and calcium chloride on the osmotic properties of hyaluronic acid solutions can be accounted for by their contributions to the ionic strength. Nevertheless, the effects of coiling and self-association can be stimulated in solution by added salt.     

多羟基化合物水溶液渗透系数的测定

The determination of the osmotic coefficients of the aqueous solution of polyhydroxylated compounds such as glycol, glycerol, sucrose and glucose by Vapour Pressure Osmometry at 313, 323 and 333K was carried out over the concentration range of 0.0-2.1mol﹒kg-1 and 0.0-2.0 mol﹒kg-1 respectively. By using a linear least-square fitting routine, the osmotic coefficients were fitted by a simple polynomial equation, It was found that the relation between the experimental results of molal osmotic coefficients Φ and the mass molal concentration of the solution m are in agreement with that from the polynomial fitting at different temperature. Factors which influence the osmotic coefficient such as the number of hydroxyl of polyhydroxylated compounds or the molecule weight of the solute molecules should be further studied, this work will also contribute to the studies of other thermodynamical properties of the aqueous solution of polyhydroxylated compound.     

MX—NX2和MX—NX3电解质水溶液的热力学研究

本文用Pitzer方程研究相同阴离子的非对称性混合电解质溶液的热力学性质,讨论了高次静电项(~Eθ_(ij)、~Eθ′_(ij))所产生的效应。引入混合参数(θ_(ij))和离子强度(Ⅰ)的关系式,估算了25℃时MX-NX_2和MX-NX_3电解质水溶液的Pitzer混合参数~Sθ_(ij)~(0)、~Sθ_(ij0~(1)和φ_(ij)k,其计算值和文献值吻合。     

H2O+KCl(饱和)+NaCl+NH4Cl的等压研究

在298.15K条件下采用等压实验方法对KCl饱和的四元水溶液体系H2O+KCl(饱和)+NaCl+NH4Cl及其两个三元亚系H2O+KCl(饱和)+NaCl和H2O+KCl(饱和)+NH4Cl进行了研究.以NaCl或CaCl2水溶液为参考溶液,测定了不同水活度条件下该四元水溶液的渗透系数及水活度.实验结果表明,该四元系与其两个三元亚系之间存在着简单的共性,在实验误差允许范围之内,该四元系的等压行为符合类理想溶液模型.     

新型压差式吸附式制冷机的设计

设计了一种以太阳能为驱动力,利用渗透压将水分从蒸发器端传输到冷凝器端的压差式吸附制冷机.水分先在蒸发器端被吸附板吸收,再通过渗透压自动运输到最后环节段,并被膨胀物质间歇式地挤压出吸水材料,进入冷凝器,从而保证水分不断从蒸发器抽出,产生制冷效果.通过改变太阳能制冷系统的四通换向阀的开启方向,实现吸附式制冷系统的连续制冷.     

On the thermodynamics of the McMillan–Mayer state function

The osmotic second virial coefficient is a key parameter in light scattering, protein crystallisation, self-interaction chromatography, and osmometry. The interpretation of the osmotic second virial coefficient depends on the solution theory. On the macroscopic level an expansion of the osmotic pressure is employed. A common statistical interpretation of the osmotic second virial coefficient of the expansion employs the McMillan–Mayer framework and the potential of mean force to characterise the solute–solute interaction. Supplementary to the statistical interpretation, it may be advantageous to develop the McMillan–Mayer framework in a classical thermodynamic context for which we develop the relationship between the state function of the McMillan–Mayer framework and the Helmholtz state function.     

Thermodynamic studies of binary methanol and ethanol solutions of 1-dodecanol and 1-tetradecanol at 25°C

The osmotic coefficients of binary methanol and ethanol solutions of 1-dodecanol and 1-tetradecanol wer measured at 25°C up to 8 mol-kg^–1 in methanol and 5.5 mol-kg^–1 in ethanol. The activity coefficients of the solute were calculated from Bjerrum's relation. From the osmotic and activity coeficients the excess Gibbs energies of solution as well as the respective partial molar functions of solute and solvent and the virial pair interaction coefficients for the excess Gibbs energies were calculated. In addition, the difference in the Gibbs energy of solvation for the solvent in solution relative to the pure solvent was calculated, as well as the partial molar volumes and excess partial molar volumes of solutes at infinite dilution, and the coefficients of pairwise contributions to the excess volume were determined. The thermodynamic parameters obtained are discussed on the basis of solute-solvent and solute-solute interactions.     

Effect of operating conditions on water transport during the concentration of sucrose solutions by osmotic distillation

A recent membrane technique, osmotic distillation (OD), is used to concentrate binary water–sucrose solutions at ambient temperature under atmospheric pressure. The principle is based on the extraction of water vapour from a dilute aqueous solution, which is put in contact with a hypertonic salt solution by means of a macroporous hydrophobic membrane. The concentration difference between both solutions translates into a transmembrane vapour pressure drop, that constitutes the driving force for mass transfer. An experimental device is designed at laboratory scale for this study, allowing achievement of vapour fluxes of 10 kg m⁻² h⁻¹ under standard conditions. The effect of various operating parameters on vapour flux is studied. The solute content results in the most influencing variable via water activity in brine and via viscosity in sugar solutions. The effect of concentration polarisation on the brine side is not negligible and would have to be taken into account for process optimisation. This phenomenon could not be quantified on the sugar solution side due to pressure drop limits of the pilot rig. Eventually, the vapour flux can be significantly increased by adding a temperature difference to the transmembrane concentration difference, when pure water is evaporated.     

Ion-specific repulsive interactions in colloidal silica dispersions evidenced through osmotic compression measurements and implication in frontal ultrafiltration experiments

Comparative osmotic compression experiments were performed on colloidal silica dispersions in the presence of various chloride salts at the same 0.01 M concentration with different counterions and highlighted the influence of ionic specificity on the resistance to water removal. These results were complemented with frontal ultrafiltration measurements that demonstrate modulation of the permeate flux according to the salt used.     

Hollow latex particles: synthesis and applications

One of the major developments in emulsion polymerization over the last two decades has been the ability to make hollow latex particles. This has contributed many fundamental insights into the synthesis and the development of structure in particles. Hollow latex particles also enhance the performance of industrial coatings and potentially are useful in other technologies such as microencapsulation and controlled release. Ever since the publication of the initial process patents describing these particles, there has been a global R&D effort to extend the synthetic techniques and applications. One prominent synthetic approach to hollow particles is based on osmotic swelling. This dominates the literature, and usually starts with the synthesis of a structured latex particle containing an ionizable core that is subsequently expanded with the addition of base. Fundamental to this approach are a sophisticated control of transport phenomena, chemical reactivity within the particle, and the thermoplastic properties of the polymer shell. Hydrocarbon encapsulation technology has also been employed to make hollow latex particles. One approach involves a dispersed ternary system that balances transport, conversion kinetics, and phase separation variables to achieve the hollow morphology. Other techniques, including the use of blowing agents, are also present in the literature. The broad range of approaches that affords particles with a hollow structure demonstrates the unique flexibility of the emulsion polymerization process.