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

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.