DILUTE-SOLUTION PROPERTIES OF PULLULAN BY DYNAMIC LIGHT-SCATTERING

Abstract

Pullulan, produced by the fungus Aureobasidium, has been studied in dilute solution by viscometry, static low angle light scattering and dynamic light scattering at temperatures of 25, 40, 60 and 80-degrees-C. The samples used were fractions obtained by partial hydrolysis of native pullulan and successive fractionation with ethanol. The mass-average molar mass, M(w), of the studied pullulans were in the range of 1.67*10(5) to 1.0*10(6) g/mol. The translational diffusion coefficient at infinite dilution, Do, was obtained from the reduced first cumulant of the intensity autocorrelation function of the light scattered by extrapolation to zero scattering angle and zero polymer concentration. The activation energy of diffusion, E(D), of pullulan macromolecules was calculated from Do = D(o)exp(-E(D)/RT). It was found that in the given temperature range E(D) = 16.5 /- 0.5 kJmol-1 for all samples.