The onset temperature To of the transition at a fixed KC/gelatin
ratio, as a function of total biopolymer concentration, is shown
in Fig. 6a.To gradually decreases as the concentration decreases.
Below the concentration of 0.4%, the complex coacervate could not
be visually observed at 30◦C under CLSM. With decreasing biopolymer concentration, long-range electrostatic repulsion becomes more important, and the electrostatic attraction between KC and
gelatin is weakened as well as the hydrogen bonding. It again suggests that hydrogen bond interaction is closely related with the electrostatic interaction. The observation that high ionic strength,
high pH, and low concentration all lower theTodemonstrates that
the transition from the associative phase separation dominated by
electrostatic interaction to the one reinforced by hydrogen bonding should occur on the premise of the existence of electrostatic interaction