Intrinsic viscosity-molecular weight relationship and hydrodynamic volume for pullulan

A numerical method for determination of Mark-Houwink-Sakurada (MHS) equation constants, a and K, was tested with success for two series of pullulan standard samples having narrow and broad molecular weight distributions (MWD) and taken into account their polydispersity. Different solvents, which were used to determine the intrinsic viscosities and the viscometric constants, a and K (Published in the literature for pullulan), were compared. The various parameters affecting the constants are discussed. The procedure to determine the correct value of the hydrodynamic volume for pullulan was also described. This study resulted in the following MHS equations for narrow and broad MWD series of pullulan samples with M-w in the range of 5-1000 kDa: [eta] = 1.990 X 10(-4) M-v(0.667) = 1.990 X 10(-4) q(MHS)M(w)(0.667) = 1.956 X 10(-4) M-w(0.667) (Narrow MWD) [eta] = 2.263 X 10(-4) M-v(0.657) = 2.263 X 10(-4) q(MHS)M(w)(0.657) = 2.056 X 10(-4) M-w(0.657) (Broad MWD) where q(MHS) is the polydispersity correction factor and [eta] is the intrinsic viscosity in dL g(-1). The plot of log K versus exponent a was linear and inversely related. This curve was used to estimate the constant K for pullulan with a known exponent a. Among various reported solvents, the diluted aqueous salt solutions have more advantages than other solvents. (c) 2006 Wiley Periodicals, Inc.