LASER LIGHT-SCATTERING-STUDIES OF PACHYMAN

Three fractions of a pachyman sample extracted from poria cocos sclero tium in both Me2SO and a 0.5 N NaOH aqueous solution were investigated by static and dynamic laser light scattering (LLS). In static LLS, th e angular dependence of the excess time-average scattering intensity l ed to the weight-average molecular weight M-w, while in dynamic LLS, t he Laplace inversion of a precisely measured intensity-intensity corre lation function resulted in a translational diffusion coefficient dist ribution 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 corre sponding molar mass distribution F(M). We found that the ratio of:he r adius of gyration to the hydrodynamic radius was greater than 2, indic ating 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 Sci ence Ltd. All rights reserved.