ABSTRACT
The complexation between two oppositely charged polyelectrolytes (PE) can lead liquid-liquid (complex coacervates, CC) or liquid-solid (solid precipitates, SP) phase separations. Herein, the effect of pH (2-11) and ionic strength (I, 0.05-1.0 M KCl) on the associative interactions between chitosan (QL)-alginate (SA) and QL-Pectin (Pec), polysaccharides widely used in biotechnology field, is described. pH and I, exhibited significant effect on the structure and phase transitions by modifying the ionization degree (α), pka, and associative interactions between PE. Onset of binding was established at pHc 9, while continued acidification (pHτ 5.8) led to simultaneous CC and SP exhibiting a maximum turbidity in both systems. At pHδ 4.0, QL-Pec showed preferably CC structures whereas QL-SA maintained the CC and SP structures. At pHω 2, the associative interactions were suppressed due to the low ionization of Pec and SA. I (1.0 M) significantly diminished the interactions in QL-Pec due to charge screening. Molecular weight, second virial coefficient, hydrodynamic size, ionizable groups, and persistence length of polyion, influenced on the phase behavior of QL-Pec and QL-SA systems. Therefore, CC and SP are found simultaneously in both systems, their transitions can be modulated by intrinsic and environmental conditions, expanding the functional properties of complexed polysaccharides.
