A single monomer difference can impact the nanostructure output of precision oligo(phosphodiesters)

Abstract

The morphology of supramolecular materials is usually dictated by directional intermolecular interactions. However, the impact of the precise monomer sequence – their order along the polymer chain, localization, and number – on these interactions has rarely been explored in non-biological polymers. In this work, we used combinations of hydrophilic, lipophilic, aromatic, and fluorophilic monomers to synthesize a library of monodisperse, sequence-defined block co-poly(phosphodiester)s that self-assemble into complex structures. Automated and accurate control over monomer sequence allowed us to systematically vary the degree of polymerization, the ratio of oligomer blocks, the chemical composition and orthogonal supramolecular interactions, and examine how these influence the self-assembly behaviour. Remarkable morphological changes were caused by very small differences between polymers: for example, a single monomer unit determined whether spheres or nanosheets formed; and inverting the block sequence in multi-block copolymers caused a dramatic increase in micelle size. Conventional polymerization does not allow the exploration of these subtle variations in polymer sequence or composition. The ability to rapidly generate a variety of oligomers with subtle differences in their sequence enables a systematic study of the supramolecular chemistry of precision oligomers and paves the way for the rational design of functional, sequence-defined polymers and their assemblies.