Modeling the Phase Separation Dynamics of Binary Vitrimer Networks

The thermodynamic immiscibility of most polymers presents a significant challenge in plastic recycling, necessitating costly separation of missed waste streams. While traditional compatibilizers can arrest bulk phase separation, the resulting domain interfaces often compromise material performance, making strategies that promote molecular-level mixing highly desirable. Vitrimers, which are polymer networks containing dynamic covalent bonds, offer a unique pathway to facilitate this molecular-level mixing by enabling chains to exchange partners and rearrange across interfaces, allowing for intermediate properties between the original blended components.

Here, we investigate the early-stage phase separation process of binary vitrimer networks by combining simulation, theory, and experiments. It is found that the introduction of dynamic covalent bonds that crosslink chains of different polymers in solution can create homogenous blends with long term stability, depending on the bond exchange kinetics. Our model captures the critical interplay between bond exchange rate, segregation strength, and degree of crosslinking on phase separation kinetics, with the major conclusion of sufficiently slow bond exchange being able to kinetically trap the system in a mesoscopically homogeneous state. This framework provides qualitative agreement among theory, simulation, and experiments, establish a foundation for engineering reprocessible polymer blends from otherwise immiscible components.