Dynamic and static light scattering experiments have been performed at room temperature on sodium alginate ( ( M ) , = 1.9 X lo6) in the concentration range 0.2-2 g/L and in the ionic strength range 4.4-95 mM. By the introduction of a simple method based on the Schwarz inequality we have (1) compared various moments for the distribution of the radius of gyration and of the molecular weight, (2) obtained the value 10 f 6 nm for the Kuhn statistical segment, and (3) obtained from both diffusion and viscosity measurements values for equivalent-sphere parameters, which, within large errors, are in agreement with predictions by the Kirkwood-Riseman theory. Interaction properties as reflected in the values for virial coefficients and in the shapes of the photon correlation functions are discussed. Volume ABSTRACT: Angular scattering functions, P ( p ) , have been computed for subchains located in the middle and at the end of a polymethylene chain. The rotational isomeric state model developed by Flory and co-workers
We have measured intensity correlation functions for a water suspension of charged polystyrene particles in the ranges: 0.84×107–3.13×107 m−1 for the scattering vector q, 1 μs–3 ms for the delay time, and 0.15–2.1 mg/cm3 for the concentration. At low ionic strength the functions show an initial decay as well as a long time decay, characterized by the effective diffusion coeficients Deff and DL, respectively. Both Deff and DL have a minimum at the same q value and Deff scales with the inverse static structure factor. The data are analyzed using a model in which a particle is diffusing within a diffusing cage yielding values for their diffusion coefficients and for the ’’free’’ transit time of the particle in the cage. Attempts are made to correct the data for the effect of multiple scattering.
A spectrometer for the detection of laser light scattered by thermally excited capillary waves at fluid interfaces is described. Its optical system makes possible precise observations at capillaly mode wave numbers high enough to avoid significant effects of instrumental resolution and permits the beam to be incident upon the fluid interface through either of the two adjacent fluid phases. Its performance was tested on the following three model systems at 20.C: the free surfaces of water and 2-butano1, representing the oscillatory and critically damped capillary wave regimes respectively, and the interface between mutually saturated phases of these two liquids, representing the non-oscillatory regime. Accessible wave numbers for which effects of instrumental resolution were insignificant ranged between approximately 1 x lo5 and 5 x lo5 m-'. Values obtained for surface and interfacial tensions and viscosity agreed well with those obtained using a high-accuracy Wilhelmy plate tensiometer and a capillary viscometer.
We have performed scattered light intensity autocorrelation measurements on a Winsor type microemulsion system composed of brine, cyclohexane, SDS and a mixture of 1-butanol and 1-pentanol. At high cosurfactant concentration, where the microemulsion phase was considered to consist of individual, spherical water-in-oil droplets of relatively low droplet volume fraction, the autocorrelation functions were observed to be essentially single exponential, as expected. Above a certain droplet volume fraction, however, additional decay modes were observed to enter the correlation data. These modes were interpreted to be due to rotation and/or internal motion of droplet aggregates.
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