Structural transition induced by physicochemical parameters during complexation and coacervation of Poly-L-Ornithine with poly-(sodium 4-styrene sulfonate)

Abstract

We present investigations of the structures and properties of the complex formed by a strong polyanion: poly-(sodium 4-styrene sulfonate) (PSSNa) and weak polycation: poly-L-ornithine (PLO) by combining dynamic light scattering (DLS), ultra-small-angle light scattering (USALS), turbidimetry, and zetametry techniques. The mixtures of polyelectrolytes were controlled in several ways: by the change of pH, modifying the mass ratio, the temperature, and adding divalent salt. Under these conditions, the hydrodynamic radius R_H, the viscosity η, the radius of gyration R_g, and the fractal dimension D_f were determined. The maximum charge difference of biopolymers stock dispersion was displayed at pH 3.3 and at mass ratio equal to 1. The screen of electrostatic interaction shows a high contribution of hydrophobic interaction at large salt concentration to form the coacervates and the effect of temperature and ionic strength highlighted the strongly hydrophobic character of mixture. The results allowed us to conclude that the complexation was controlled by electrostatic interactions between opposites charges.

Keywords:

• Poly-L-ornithine
• complex coacervation
• core-shell
• dynamic light scattering
• ultra-small-angle static light scattering
• fractal dimension