Method of measurement of liquid-liquid phase transition parameters in aqueous solutions of amphiphiles

FIELD: measurement equipment.

SUBSTANCE: invention relates to a boundary area between physics, chemistry and biology and can be used in scientific and industrial laboratories for determination of parameters of phase transition in water and influencing conditions (pressure, temperature), influence of substances and fields. The method of measurement of parameters of liquid-liquid phase transition in amfifil water solutions by measurement of thermal effect of amphiphile solution dilution by PEO solutions depending on amphiphile concentration is offered.

EFFECT: improvement of reliability of identification and separation of two oscillating states of the system.

4 cl, 1 dwg


The invention relates to a border area between physics, chemistry and biology. Can be used in scientific and industrial laboratories to determine the parameters of the phase transition in water and influence of the conditions (pressure, temperature), additives, substances and fields. This data is judged on the use of surfactants in various industries and agriculture.

The known method of measuring the parameters of the phase transition liquid-liquid (L-L-go) in aqueous solution (patent RF 2433386). The method allows to measure the average concentration of the phase transition or the critical micellization concentration (CMC) and the degree of cooperativity, the area of concentration, where the transition occurs, the depth of the transition. Furthermore, it is known (Huang et al. // PNAS. 2009. V. 106. P. 15214) that the water on the scale of approximately 1 nm forms at room temperature shimmering fluctuations (clusters) low density with strict tetrahedral coordination (LDL) and high density fluctuations with broken H-bonds (HDL), which are in balance.

The appearance amphiphiles in water shifts the equilibrium towards formation of clusters of LDL. Upon reaching the CMC in water is achieved, the average concentration of L-L transition. Water clusters oscillate between clusters of LDL and HDL concentration in the transition region. Oscillation of ensembles of clusters of water soprovojdayut� oscillation ensembles of two types of micelles (J. A. Mirgorod // Zhurn. structure. chemistry. 2008. Kzt49. P. 920). Oscillations in ensembles of water clusters and micelles occur quickly 103-10-8C. Devices can not yet be fixed (split) in time existence of a shimmering clusters and micelles. Methods and small-angle x-ray scattering reveal only spherical or ellipsoidal micelles amphiphiles (Cabane V. et. al. // J. Physique. 1985. V. 46. P. 2161).

The known method (patent RF 2433386) does not identify two oscillating system state.

An object of the invention is to provide a method of identification (visualization) and separation of the two oscillating States of the system (energy distributions of the ensemble of clusters).

The technical result according to the invention is achieved by dilution of a solution of amphiphile in the field of critical micelle concentrations of the solution of polyethylene oxide (PEO) and measurement of thermal effect of dilution depending on the concentration of amphiphile. Prepare a solution of amphiphile with a concentration above its CMC. In other volumetric glassware prepare a solution of PEO, about 100 times more dilute than the solution of amphiphile in weight percentage. For experiments take PEO with a molar mass of from 2000 to 100,000 g·mol-1. It is desirable to take PEO with a narrow molecular weight distribution. On isotherme�Eskom calorimeter spend thermometric titration. By measuring thermal effects depending on the concentration of amphiphile curve thermometric titration (see drawing). On the curve there are two opposite thermal effects of the "hump". They indicate the existence of two processes in the area of concentration micellization amphiphiles. From small concentrations occurs first endothermic process, and then exothermic. Different processes reflect the interaction of PEO with two types of micelles, the formation of which prevails in different areas of concentrations of amphiphile. With PEO molar mass, lesser 2000 g·mol-1two processes are not visualized. With a molar mass greater then 100,000 g·mol-1they appear bad. Solutions during the titration must be transparent. They should not form a precipitate or become cloudy.

Humps reflect the distribution of the ensemble of clusters energy (enthalpy) dilution in the concentration range of amphiphile in States A and B. When each of multiple concentrations in the range L-L-transition is the distribution of States A and B. Thermometric curve shows the cumulative distributions for the concentrations. Temperature, pressure, electrolyte, electromagnetic and acoustic field affect this distribution. From 25 to 5°C humps increase and bring�I, and at 65°C disappear.

The invention is illustrated by an example. Prepare a 10% (wt.) a solution of sodium dodecyl sulfate (DSS) and 0.1% (wt.) a solution of PEO molar mass of 3350 g·mol-1. KCM DCS 8·10-3M. isothermal microcalorimetry spend thermometric titration of a solution of PEO solution DCS at 15°C. Then build a graph of thermal effect on the concentration DCS (see drawing). The drawing on the interfaces direct with curves define the beginning of c1=4·10-3M and end with C2=28·10-3M L-L transition. Two s-shaped curves - average concentrations of cA=6·10-3M, cB=22·10-3M and enthalpy of formation of the ensemble of clusters in the position AND ΔHA=10 kJ·mol-1In ΔHB=-4 kJ·mol-1. Concentrations are determined so that the area of each triangle below the function and above the function ΔH(x) were the same.

Thus, using supplements PEO in the solution of amphiphile and measurement during the additive thermal effect of dilution can be clearly seen models shimmering clusters of solutions amphiphiles in the field of micelle formation from c1to c2and to determine their energy options. This phenomenon allows the simulation of relaxation processes in solutions amphiphiles in the study, for example, penetration of drugs through the skin under the influence of ultrasound or HC�increase oil production under the influence of the electromagnetic field.

1. Method of measurement of parameters of the phase transition liquid-liquid in aqueous solutions amphiphiles measurement of thermal effect of dilution of the solution of amphiphile solutions PEO, depending on the concentration of amphiphile.

2. A method according to claim 1, characterized in that the take polyethylene oxide with a molar mass of 2000-100000 g·mol-1.

3. A method according to claim 1, characterized in that as parameters of the phase transition determine the region of concentrations where phase transition occurs, the average concentrations of the two distributions of ensembles of clusters, the enthalpy of the distributions of the two ensembles of clusters.


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