Having established the setup, we examined the response of our system to the pH gradient in detail. Notably, the states in Fig were achieved with a small delay compared to the instance when the pH was changed. That the PEs and PEC require time to be re-dissolved or formed, respectively, provides us with a window wherein we could examine the influence of the gradient on PEC formation. Particularly, the steady states of Fig. are visualized by averaging the signal of the last 5 min of each time interval. Fig. shows that the local minima, i.e., the point at which the highest concentration of the PAH-PAA complex is formed, are slightly different for the positive (∆pH/∆t = +1 h -1 ) and negative gradient (∆pH/∆t = -1 h -1 ). Specifically, the PAH-PAA complex was formed at higher pH values for the positive gradient (7.5 < pH < 8.5) than for the negative gradient (6.5 < pH < 8.0). That the direction of the gradient determined the optimal pH for the PAH-PAA complex suggests that the fate of the complex could depend on a preceding state.