We analyze the scaling properties of pH-dependent shear modulus spectra of complex coacervates made of weak polyanions and strong polycations. For the first time, we report on a "time-pH superposition principle". This principle implies that the charge density in complex coacervates made of not fully charged polyions only influences the time scale of the relaxation dynamics, but not the mechanisms of the underlying dynamics.

pH‐dependent growth laws of the mass coverage Γ(n) of poly(diallyldimethylammonium) chloride and poly(acrylic acid) (PAA) layer‐by‐layer films are analyzed by Quartz Crystal Microbalance‐D. (Attenuated Total Reflection)‐FTIR spectroscopy shows a degree of dissociation of acrylic acid groups in the films identical to that in solution. Apart from pH‐regimes of differently pronounced exponential and linear growth, the corresponding kinetics indicate pH‐dependent adsorption, reorganization, and diffusion processes. As the thickest films form with almost uncharged PAA (low pH), the results can only partly be explained by the dissociation degree of PAA in the film. For intermediate and high pH values chain interdiffusion as a mechanism for nonlinear growth is strongly dependent on the charge density of the PAA chains. However, at low pH other types of interactions, most likely ion–dipole interactions, play a major role in the multilayer growth. Furthermore, a change in the symmetry of growth can be observed in the low to intermediate pH range. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 425–434

The layer‐by‐layer formation of polyelectrolyte multilayer films based on poly(l‐lysine) and hyaluronic acid (PLL/HA) is investigated in situ as a function of the pH value employing the quartz crystal microbalance with dissipation. By the use of the Kelvin–Voigt viscoelastic model, the film thickness, the complex viscosity, and the complex shear modulus are obtained as a function of the single layer number and pH. For all investigated pH values, PLL/HA films show an exponential growth behavior. However, in different pH regimes the exponentiality, represented by the exponential factor of the respective fit function, is more or less pronounced. Toward low or high pH values, PLL interdiffusion causing exponential growth is less relevant for the increase in mass coverage, though in the high (pH > 9) and the low (pH < 5) pH range thicker (PLL/HA)4 multilayers form. Here, the films are less viscous and less elastic compared to polyelectrolyte multilayers formed at intermediate pH (5 ≤ pH ≤ 9) conditions. Film thickness, viscosity, and elasticity do not only change with pH but also with the kind of the terminating layer. This odd–even effect is caused by the diffusion of PLL into and out of the multilayer film.