The initial BC concentration in the resulting colloidal susp

The initial BC concentration in the resulting colloidal suspension (BC CS), determined by Tipifarnib to constant weight, was w2=0.305g/g. The subsequent samples of aqueous BC CS with lower BC concentrations were obtained by adding distilled water to the initial colloidal suspension. The initial BC CS and its aqueous solutions were a gel system with non-settling colloids. The dielectric permittivity ε of BC CS was measured in the range of BC concentrations 0.016≤w2≤0.305g/g in a dielectric measuring cell (Fig. 2), a bottle whose cylindrical tank (“ground”) 1 and disc-shaped potential electrode 2 were made of titanium. Glass beads 3, determining the distance between the electrodes, were mounted on the lower surface of the potential electrode. The bottle\'s cap 6, fitted to the tank, was made of pyrex glass. Glass stopper 7 with sealed glass tube 5 and platinum needle 4 that was part of the upper electrode was connected to the upper part of the cap by means of a ground-glass joint, centering the electrode in the cell. Thermocouple 8 was inserted into the bottom of the tank. The cell\'s interelectrode capacitance C0 was determined by the standard method using nonpolar solvents. C0 and the fill volume of the cell were 15pF and 4cm3, respectively. To exclude the effect of near-electrode polarization on the dielectric parameters of the water systems under consideration, the measurements of the electrical capacitance were performed at a frequency of 1MHz (with the LRC E7-12m). The measured dielectric permittivity ε of the aqueous suspension at this frequency can be taken to be a quasistatic value, since the maximum dielectric loss factor ε″ of water is at a frequency of about 5·109Hz. The frequency dependence for ε″ was measured with the LCR Meter 4270 (Novocontrol) in the 50Hz – 990kHz frequency range. The temperature for the measured macroscopic dielectric parameters of the water systems was 295K. X-ray studies of the initial and disintegrated dried films were carried out with a DRON-2 setup and an RKB-86 X-ray camera. CuKα-radiation was used.
Experimental results and discussion The dipole moment and the volume of the BC colloid. Fig. 3 shows the electrical capacitance dependence of the cell filled with BC CS versus the mass concentration w2. This suspension was pre-disintegrated at two blade rotation rates: 1.5·104 and 2.0·104rpm. It can be seen from Fig. 3 that the capacitance concentration curves 1 and 2 exhibit a generally non-linear character. However, these dependences are symbate and linear in the segments of the curves where the concentration is less than 0.15g/g, indicating that the stoichiometry of BC colloids in the suspension remains constant in this concentration range. The С (w2) curves reach plateau as the w2 values exceed 0.17g/g, collapsing into a single curve for the BC suspensions of both samples. This result points to the common character of the morphology in BC CS, despite the different disintegration rates, and the common trend towards further macrocoagulation. Fig. 4 shows the dependence of the permittivity ε12 of BC CS on the molar concentration of BC, х2, in the region where the dependence is linear. The linear nature of the ε12 concentration dependence makes it possible to use Buckingham\'s statistical theory of dielectric polarization [18] to determine the orientational dielectric polarization S12 of BC colloids in the suspension. It should be kept in mind that by its chemical structure, BC is a pure product whose macromolecules consist only of cellobiose units. For this reason, we were able to use Buckingham\'s statistical polarization theory for a two-component system comprising molecules of cellobiose and water to estimate the dipole moments of the BC colloid. Below, we briefly describe a scheme for calculating the orientational polarization of BC CS and the dipole moment of a single colloid (relying on our previous studies on dipole moments of cellobiose and water by the dielectric method [22]).