Laser light-scattering studies of pachyman

Three fractions of a pachyman sample extracted from poria cocos sclerotium in both Me2SO and a 0.5 N NaOH aqueous solution were investigated by static and dynamic laser light scattering (LLS). In static LLS, the angular dependence of the excess time-average scattering intensity led to the weight-average molecular weight M-w, while in dynamic LLS, the Laplace inversion of a precisely measured intensity-intensity correlation function resulted in a translational diffusion coefficient distribution G(D). A combination of static and dynamic LLS results enabled us to establish a calibration of D (cm(2)/s) = 3.6 x 10(-4) M-0.674. Using this calibration, we were able to convert each G(D) into a corresponding molar mass distribution F(M). We found that the ratio of:he radius of gyration to the hydrodynamic radius was greater than 2, indicating that the pachyman chains have an extended conformation in Me2SO. Our results also revealed the formation of large pachyman aggregates with a loose structure in aqueous NaOH solution. (C) 1998 Elsevier Science Ltd. All rights reserved.