Determination by Means of Light Scattering

The study of light scattered by a nematic sample allows the determination of the viscosities 7]j(q) and Tj Cg) (see Eqs. 17 and 18), which are mainly determined by the rotational viscosity coefficient yj, but also contain other coefficients because of the backflow. In principle, all coefficients can be determined with different accuracies by a suitable choice of the scattering geometry. The influence of the small coefficient Oi is normally neglected. For 4-n-pentyl-4 -cya-nobiphenyl, Chen et al. [93] found the following values at 25 °C 03=-0.086, a3=-0.004, a4=0.089, c%=0.059 and o = -0.031 Pa s. 

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Determination of the exponent a of the scaling law AAg == M (dilute solution) The Xab parameter (or AA2) was determined by means of light scattering for the PS-PDMS-toluene, PMMA-PDMS-chloroform and PS-PVAc-styrene. The method used here was proposed by Inagaki, and is... 

Results from AFM studies are supported by light-scattering data. The particle size distribution in the MDMO-PPV solutions can be analyzed by means of light-scattering measurements using a Microtrac Ultrafine Particle Analyzer. This technique allows us to determine the particle size (PS) in solutions. It can be expressed as a number distribution or a volume distribution. The results for MDMO-PPV dissolved in toluene and chlorobenzene with different concentrations (0.0625%, 0.125% and 0.25%) are given in Table 5.1. 

Determination of Micellar Weight Determination of micellar weights for DSS in anhydrous and hydrous hydrocarbon solutions has been made by means of light scattering (34). 

Benoit H. Determination of the dimensions of anisotropic macromolecules by means of light scattering. Makromol... 

Due to the dark color of alkali lignins, their molar masses cannot be determined by means of the light-scattering method. However, as shown by Figure 10, elution with sodium hydroxide also brings about a consistent elution pattern of lignin sulfonates and polypeptides. It is assumed that this also applies to the kraft lignins. 

The molecular weight of the standards is supplied by the producers, either with a single value which should correspond to that of peak maximum, or with a complete characterization data sheet containing the values of and determined by osmometry and light scattering. In the latter case, the peak molecular weight to be inserted in the calibration plot is the mean value A typical calibration curve for a three-... 

Mean hydrodynamic diameters of vesicles (liposomes, nanospheres, nanobeads) can be determined by dynamic laser light scattering, e.g. the NICOMP 380 particle sizing instrument, Particle Sizing Systems (Sta. Barbara, CA, USA). 

The molecular weight of PVA is determined by osmometry or light scattering of an aqueous solution of PVA. Often, PVA is acetylated to polyvinyl acetate and the measurement of molecular weight is carried out by means of solution in organic solvents, because acetylation in ordinary conditions does not change the DP. 

For the present fluid-mechanical tests a homologous series of polyacrylamide (PAAm) samples was used whose mean weights, of the molar masses were determined by means of a low-angle laser-light-scattering photometer. The PAAm samples exhibit virtually the same molecular weight distribution Myy/Mn = 2.5 the intrinsic viscosity [ 7 1 was deter-minded in a Zimm-Crothers rotational viscometer, since the polymer solutions are subjected to a very low shear rate in this instrument. The porous media flow tests were carried out with the aid of an instrument such as described in Refs. [1, 2]. Reference is also made to these studies as regards the test procedure and evaluation of the measured data. 

Thus, the ratios (A + 4/3/i)// and pjf can, in principle, be obtained from the time correlation of scattered light. The meaisured integral intensity of scattered light (see Equation 2.3 40) (whose theoretical value is calculated from Equations 132 and 133 at t - 0) gives the quantities K + 4/3/i and p (cf. Equations 2.3-39,-40, 43,-48). Hence, all the elasticity parameters of the gel A, p, and / can be determined by means of the polarized/depolari ed scattering technique only. 

The kinetics of diffusive mass transfer at 1050 to 1290C were determined by means of laser light-scattering studies of the levelling of surface irregularities. The results for the (100) plane could be described by ... 

The optical constants of the substances investigated always constituted an uncertainty in the calculations Gribnau has attempted vice versa to calculate the optical constants from the measured light scattering His results agreed in a satisfactory way with, among others, values determined by means of reflection measurements ... 

The Rayleigh ratio as defined by Equation (24) has a precise meaning, yet it is a quantity somewhat difficult to visualize physically. After we have discussed the experimental aspects of light scattering, we shall see that Re is directly proportional to the turbidity of the solution when turbidity is the same as the absorbance determined spectrophotometrically. 

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