Creation of Segmented Platelets with Diverse Crystalline Cores Using Double Crystalline Triblock Copolymers

Abstract

Two-dimensional (2D) platelet structures with uniform dimensions and spatially defined diverse cores are highly sought but are still challenging to access. Living crystallization-driven self-assembly (CDSA)-seeded growth enables the creation of uniform 2D core–shell nanomaterials with diverse core compositions via sequential epitaxial crystallization of block copolymers. Nevertheless, general limitation of the growth process to strict requirements of heteroepitaxial crystallization is a major obstacle to the formation of segmented nanoparticles with extended diverse core chemistries. Herein, we introduce a strategy of using double-crystalline triblock copolymers, such as poly(ε-caprolactone)-block-poly(p-dioxanone)-block-poly(N,N-dimethyl acrylamide) (PCL-b-PPDO-b-PDMA), as bridges to create segmented platelets with compositionally distinct cores. The epitaxial crystallization of the PCL block excludes the PPDO block, forming out-of-plane PPDO crystals that seed subsequent epitaxial crystallization of the added PPDO unimer, producing flat-on quasi-square PPDO crystals. Meanwhile, the less-defined orientation of PPDO crystals has confirmed the presence of flat-on epitaxy between PCL and PPDO. For comparison, PCL-b-PHL (PHL = poly(ζ-heptalactone)) forms in-plane crystals with a strictly defined orientation via edge-on epitaxy due to the cocrystallization of PCL and PHL. Therefore, this approach provides a novel route to construct precisely controlled segmented 2D platelet structures with chemically distinct cores and tunable functionalities, an extension to expand the precise design of complex nanoparticles.