title: Light scattering and crossover critical phenomena in polymer solutions.
abstract: An accurate photon-correlation spectrometer capable of measuring scattered light at two fixed scattering angles simultaneously in the temperature range from 10 to 120 degrees C is described. For the detection of the correlation function of the scattered light both an original correlator (PhotoCor-SP) with a linear-time-scale channel spacing and an ALV GmbH correlator (Model ALV-5000) with a logarithmic-time-scale channel spacing are used. High-resolution static and dynamic light-scattering measurements near the critical point of a polystyrene solution were performed with this instrument. The static-intensity measurements reveal that the crossover from mean-field to Ising behavior occurs at a temperature at which the correlation length of the critical fluctuations becomes equal to the radius of gyration of the polymer molecule. We found that the wave-number dependence and the temperature dependence of the diffusion coefficient of the concentration fluctuations are not consistent with existing theory for critical dynamics in low-molecular-weight liquid mixtures.
authors: J
authors: J
authors: Jacob
authors: M A
authors: MA
authors: Anisimov
authors: J V
authors: JV
authors: Sengers
authors: V
authors: V
authors: Dechabo
authors: I K
authors: IK
authors: Yudin
authors: R W
authors: RW
authors: Gammon