Growth Mechanism of Polymer Membranes Obtained by H-Bonding Across Immiscible Liquid Interfaces

Complexation of polymers at liquid interfaces is an emerging technique to produce all-liquid printable and self-healing devices and membranes. It is crucial to control the assembly process, but the mechanisms at play remain unclear. Using two different reflectometric methods, we investigate the spontaneous growth of H-bonded PPO-PMAA (polypropylene oxide-polymetacrylic acid) membranes at a flat liquid-liquid interface. We find that the membrane thickness h grows with time t as h similar to t(1/2), which is reminiscent of a diffusion-limited process. However, counterintuitively, we observe that this process is faster as the PPO molar mass increases. We are able to rationalize these results with a model which considers the diffusion of the PPO chains within the growing membrane. The architecture of the latter is described as a gel-like porous network, with a pore size much smaller than the radius of the diffusing PPO chains, thus inducing entropic barriers that hinder the diffusion process. From the comparison between the experimental data and the result of the model, we extract some key piece of information about the microscopic structure of the membrane. This study opens the route toward the rational design of self-assembled membranes and capsules with optimal properties.

Automated summary

Complexation of polymers at liquid interfaces is a promising technique for producing printable and self-healing devices and membranes. This study investigates the spontaneous growth of H-bonded PPO-PMAA membranes at a liquid-liquid interface using two reflectometric methods. The results indicate that the membrane thickness grows with time in a manner similar to a diffusion-limited process, with faster growth observed as the PPO molar mass increases. The study provides insight into the microscopic structure of the membrane and paves the way for the rational design of self-assembled membranes with optimal properties.