Uniform “Patchy” Platelets by Seeded Heteroepitaxial Growth of Crystallizable Polymer Blends in Two Dimensions

Rectangular platelets formed by the self-assembly of block copolymers in selective solvents are of interest for a range of applications. Recently, we showed that the seeded growth of crystallizable blends of a block copolymer and homopolymer yields well-defined, low area dispersity examples of these two-dimensional (2D) structures. The key feature was the use of the same crystallizable polymer segment in the seed and blend components to enable an efficient homoepitaxial growth process. Herein we demonstrate that this 2D crystallization-driven self-assembly approach can be extended to heteroepitaxial growth by the use of different crystallizable polymers with compatible crystal structures. This allows the formation of well-defined "patchy" rectangular platelets and platelet block comicelles with different core chemistries. The use of scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy provided key information on the spatial location of the components in the resulting assemblies and thereby valuable insight into the 2D heteroepitaxial growth process.