Translational diffusion of small and large mesoscopic probes in hydroxypropylcellulose-water in the solutionlike regime

摘要

Quasi-elastic light scattering spectroscopy was used to study the translational diffusion of monodisperse spheres in aqueous 1 MDa hydroxypropylcellulose (HPC) at 25 degrees C. Probe diameters d spanned 14-455 nm; HPC concentrations were 0 less than or equal to c less than or equal to 7 g/L. Light scattering spectroscopy consistently found spectra having the form g((1))(t) = (1 - A(f))exp(- theta t(beta)) + A(f) exp(- theta(f)t(beta)f). Here theta(f) and Pf refer to the ''fast'' mode; theta and beta describe the ''slow'' mode. We examine the dependence of theta, beta, theta(f), beta(f), and A(f) on d, c, scattering vector q, and viscosity eta. beta = 1 for large probes; elsewise, p and ef are E (0,1). The slow mode, with short-lived memory function, is diffusive; for large probes theta approximate to(d eta)(-1). The fast mode, with long-lived memory function, appears coupled to polymer chain internal dynamics. Probe behavior differs between "small" and "large" probes. Small probes have diameters d