Symmetric Diblock Copolymers Form Versatile and Switchable Ultrasmall Nanoparticles

Block copolymers (BCPs) can form a multitude of nanoparticles which serve as promising drug delivery systems, photonic crystals, and colloidal coatings. Recently, a new class of ultrasmall nanoparticles having a disk-like shape has been discovered. Such nanodisks were found to be next-generation anti-tumor drug carriers. However, it is unknown whether such small nanoobjects can be stimuli-responsive and be transformed into other small nanoparticles upon a change of external conditions. In this work, we discovered that nanodisks formed by symmetric diblock copolymers can transition into a variety of other ultrasmall nanoparticles that potentially possess unique optical, hierarchical self-assembly, and drug delivery properties. These transformations occur upon tuning the block-block and polymer-solvent interaction energy. For nanoparticles having larger sizes, we have predicted the existence of a novel multilayered nanodisk particle. These predictions were made by performing self-consistent field theory simulations according to a newly developed algorithm that eliminated metastable states and obtained true equilibrium morphologies. We demonstrated that ultrasmall BCP nanoparticles are extremely versatile and tunable, which will potentially establish symmetric BCPs as a platform for the production of the next-generation stimuli-responsive nanoparticles.