Opportunities and challenges for inverse design of nanostructures with sequence defined macromolecules
Accounts of Materials Research (2021)
Abstract
Self-assembly of block copolymers has a rich history and has been shown to be a versatile and robust strategy for the bottom-up fabrication of nanostructured functional materials, (1) with especially exciting applications in medicine. (2) This is due in part to the fact that even blocky sequences composed of a few monomers exhibit rich phase behavior which can be tuned to achieve exotic structures. (3,4) However, these simple patterns represent only a tiny fraction of all sequences that can be synthesized in a modern chemistry laboratory. For instance, biological proteins which may be composed of dozens of amino acids in arbitrary (and lengthy) sequences can be readily synthesized. Yet it is presently impossible to predict how these complex chemistries lead to structures without experimental or computational trial and error. While developments in block copolymer technologies have been driven by the use of mean field theory, (5) mean fields cannot resolve the detailed structures or self-assembly pathways of these molecules, instead being limited to bulk equilibrium phase diagrams. (6) Prior work has studied intrinsically disordered proteins (IDPs), which do not fold into any tertiary structures but instead self-assemble into membraneless organelles. (7) A recent Molecular Dynamics (MD) simulation study on IDPs showed that conventional thermodynamic arguments cannot explain the link between chemistry and self-assembled structure when the monomer sequence is nonblocky, even with only two types of monomers. (8) Thus, more sophisticated models are needed. We use this prior work (8) as a case study on new opportunities and remaining challenges in the inverse design of soft matter.