Leveraging inhomogeneous binding of incompatible constituents for adaptive copolymer self-assembly.

Abstract

Using a polymer field-theoretic model, we present a system containing copolymers and two distinct chemical moieties that bind heterogeneously along the copolymer chains, enabling self-assembly of a range of periodic morphologies by tuning the concentration of binder species. Our model consists of generic "guest" species, A and B, that compete to bind "host" sites on the copolymer chains. The chemical potentials of the guests control the extent of binding, and thus determine the copolymer block size and self-assembly behavior. We apply a transfer-matrix method to calculate binding profiles along the copolymers at varying conditions. The random-phase approximation is then employed to calculate quartic-order free-energy expressions for lamellar, cylindrical, and body-centered cubic phases, which are used to generate phase diagrams. This theory predicts that our single model system can access a range of stable phases without changing the polymer sequence, allowing for polymer materials with facile control over microphase segregation.