Understanding the Interfacial and Self-Assembly Behavior of Multiblock Copolymers for Developing Compatibilizers toward Mechanical Recycling of Polymer Blends

Multiblock copolymers (MBCPs) constitute a class of materials with distinctive structures and properties. Among MBCPs, linear and grafted multiblock copolymers emerge as two promising candidates for advancing the development of high-performance compatibilizers for homopolymer mixtures. However, elucidation of the underlying mechanisms for modulating their behaviors as compatibilizers remains an unresolved challenge. Here, we conducted extensive dissipative particle dynamics (DPD) simulations to study the compatibilization efficiency and micelle formation of linear and grafted multiblock copolymers in terms of the interfacial tension and self-assembly behavior. The compatibilization efficiency of all MBCPs increases with the interfacial areal concentration before reaching a plateau by reducing the unfavorable contact between homopolymers. The effect of the number of blocks of copolymers on the compatibilization efficiency is more dominant in the highly incompatible system with a high value of interfacial areal concentration. We find that there is a minimal disparity in the compatibilization efficiency between the graft and linear copolymers for weakly incompatible systems, whereas the difference is more notable for highly incompatible systems. The graft copolymer with the highest number of blocks exhibits the best compatibilization efficiency among all copolymers for highly incompatible systems. Moreover, micelle formation is a common phenomenon after the addition of copolymers due to the self-assembly behavior. We find that graft copolymers exhibit a lower tendency to form micelles compared with linear copolymers. Furthermore, we find that the micelle size of linear copolymers is larger than that of graft copolymers, suggesting a higher possibility of a copolymer phase in the homopolymer blend. Our results demonstrate how linear and graft multiblock copolymers are likely to function as compatibilizers, forming micelles due to the self-assembly behavior in the homopolymer phase as well as accumulation in the interface to reduce the interfacial tension. We anticipate that our work will be a starting point for more sophisticated in silico models of compatibilizers on the upcycling of waste thermoplastics.