Binding-Induced Bond Polarization in Polymer Solutions to Drive Micelle and Vesicle Formation

Abstract

Driving self-assembly through donor–acceptor interactions to create nanostructured materials is a key feature of supramolecular chemistry; however, the connection between molecular-level changes and larger-scale organization is still unknown. Here, we propose the concept of Lewis adduct binding-induced bond polarization, where the formation of the Lewis adduct leads to a large dipole (here estimated to be 12.5 D), significantly altering the intermolecular interactions between different species and inducing self-assembly. Specifically, a diblock copolymer, poly(2-(dimethylamino)ethyl methacrylate)-polystyrene (PDMAEMA-PS), self-assembles into nanostructured colloidal aggregates on the addition of the Lewis acid tris(pentafluorophenyl) borane (BCF) in toluene. The morphology of the nanostructured colloidal structures is controlled by tuning the block mole fraction of the poly(Lewis base) (polyLB, i.e., PDMAEMA) within the diblock copolymer, resulting in spherical micelles, vesicles, and large compound vesicles with an increasing PDMAEMA block mole fraction. The self-assembly is driven by binding-induced bond polarization during Lewis adduct formation, where the degree of bond polarization of the Lewis adducts is quantified by measuring the dielectric constant of adduct mixtures. We propose that the large dipole formed because of the Lewis adduct leads to substantial changes in the polymer–solvent interactions, driving the self-assembly. The reported findings regarding the Lewis adduct-induced self-assembly in polymer systems have far-ranging potential implications in supermolecular chemistry.