Comparative studies on molecular chain parameters of chitosans and poly(diallyldimethylammonium chloride): the stiffness B-parameter and the temperature coefficient of intrinsic viscosity

The empirical coefficient B, a measure of polyelectrolyte chain stiffness was estimated for two types of polycations: chitosans with FA (mole fraction of N-acetyl-d-glucosamine units) ranging from 0.09 to 0.21 (determined by 1H NMR method) and poly(diallyldimethylammonium chloride) (PDADMAC), in the presence of different counterions (Cl−, Br−, NO3−, ClO4−).The method relies on the measurements of the intrinsic viscosity, [η], of polyelectrolyte chains at different solution ionic strength (I). Thus, the B-parameter shows the response of the hydrodynamic volume of polyelectrolyte molecules to the salt concentration in solution (the so-called salt tolerance) referred to the [η] at I=0.1 M. The temperature coefficient of intrinsic viscosity of PDADMAC and chitosan was also determined. The comparison of the B-parameters indicates lower flexibility of chitosan than PDADMAC. The reasons for this difference are discussed.