Coacervation can be used to prepare controlled dense solutions for biomedical applications. In coacervation, liquid-liquid phase separation occurs due to electrostatic interactions from colloids [1]. This study aims to characterise the effect of different salts and their concentrations on coacervation.

The characterisation of Agar Gelatin coacervates with addition of NaCl, KCl, CaCl2 are performed under optical microscopy, atomic force microscopy (AFM), turbidimetric titration, differential scanning calorimetry (DSC), and rheological testing.

In optical microscopy (Fig. 1) where the pattern formation in Agar Gelatin Coacervate with (from left) 0.02M, 0.05M, 0.1M NaCl 50 µm. This is further defined by AFM (Fig. 2), increased dendritic pattern formation and their correlation with increasing salt concentration can be observed. Fractal dimensions can be measured.

Figure 3 shows the effect of salt on the onset of coacervation and precipitation. These results justify the theory of the effects of ‘shielding’ of the interaction from the dissociated salt ions on the coacervation process [2].

Rheological testing (Fig. 4) show viscoelastic behaviour in coacervate dense phases and also the temperatures and forces at which transitions in the structure occur. These transition temperatures correlate with results of DSC (not shown here).

Characterisation of the effect of different salts and their concentrations on coacervate formation are reported above by methods described. Further experimentation in nano-indentation would allow study of deformation characteristics. Also, surface potential mapping of the coacervate is continuing for understanding the short-range interactions in the dense phase.

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