Osmotic pressure, correlation lengths and viscosity of aqueous pullulan solutions beyond the overlap concentration

We investigate the thermodynamic, scattering, and flow properties of pullulan, a flexible non-ionic polysaccharide in aqueous solution, focusing on semidilute and concentrated solutions. We review dilute solution data for the intrinsic viscosity and radius of gyration and hydrodynamic radius of aqueous pullulan and find the Kuhn length and thermal blob size, below which the polymer chain is nearly ideal, to be 3 nm and 20 nm, respectively. We establish the scaling laws for static correlation length, specific viscosity, osmotic pressure, and osmotic compressibility across dilute, semidilute, and concentrated regions, finding that the scaling exponents align well with theoretical predictions but the crossover concentrations obtained from different methods are not consistent. The ratio between the osmotic and Ornstein–Zernike correlation lengths ξΠ/ξOZ is approximately 2.5 for aqueous solutions, similar to that observed in polystyrene in a theta solvent. This similarity may arise because the crossover concentration between the semidilute and concentrated regions c∗∗ is close to the overlap concentration c∗.