Micellization of Pee-PEO Block Copolymers in Organic Solvents for Use As Perovskite Nanoreactors

Block copolymers are made up of chemically distinct polymeric segments connected through a covalent bond. The chemical dissimilarity between segments leads to a variety of self-assembled nanostructures both in bulk and solution. Block copolymer micelles have been studied extensively due to their use in the fields of drug delivery and emulsification. The objective of the present study is to control the formation of poly(ethyl ethylene)-b-poly(ethyl oxide) (PEE-PEO) block copolymer micelles in organic solvents such as decane and squalane. The intent is to use PEE-PEO micelles as nanoreactors to grow perovskite nanocrystals, a material used to improve optical-electrical properties in solar cells and energy storage devices. As the micelle shape, size and distribution can greatly affect the stability and effectiveness of the perovskite nanocrystals, the micelle size and its distribution have been optimized by varying polymer concentration, temperature, solvent quality, and the method of preparation. Multi-angle dynamic light scattering measurements were carried out to determine the average hydrodynamic radius of the micelles and the micelle size distribution. Micelles were also characterized using small-angle X-ray scattering to evaluate the shape. Overall, the best micelles for the application were found to be prepared through direct dissolution of the polymer in decane at room temperature, surprisingly without any heating or annealing steps.