Micro- to macro-phase separation transition in sequence-defined coacervates.

Phase separation can be driven by the association of oppositely charged polyelectrolytes in solution, a process known as complex coacervation. This can manifest as macrophase separation, which arises when both polymer species are homopolyelectrolytes, or can lead to microphase separation when one or both of the charged species are block copolyelectrolytes. This is not a strict dichotomy; recently, macrophase separation was observed for a number of copolymers containing sequence-defined patterns of neutral vs charged monomers, including patterns with lengthy blocks. The specific pattern can affect the strength of this macrophase separation, yet at some block length, microphase separation is expected to emerge. In this article, we describe how to incorporate a theory of sequence-defined coacervation into self-consistent field theory, allowing the study of sequence-defined polyelectrolytes in inhomogeneous systems. We show that blocky sequences can affect electrostatically driven macrophase separation and can transition to microphase separation as the blockiness of sequences increases. This micro- to macrophase separation transition is a function of both the blockiness of the sequence, the number of blocks, and the concentration of salt.