Complex and Hierarchical 2D Assemblies via Crystallization-Driven Self-Assembly of Poly(L-lactide) Homopolymers with Charged Termini

Poly(L-lactide) (PLLA)-based nanoparticles have attracted much attention with respect to applications in drug delivery and nanomedicine as a result of their biocompatibility and biodegradability. Nevertheless, the ability to prepare PLLA assemblies with well-defined shape and dimensions is limited and represents key challenge. Herein we report access to a series of monodisperse complex and hierarchical colloidally-stable 2D structures based on PLLA cores using the seeded growth, “living-crystallization-driven self-assembly” method. Specifically, we describe the formation of diamond-shaped platelet micelles and concentric “patchy” block comicelles by using seeds of the charge-terminated homopolymer PLLA24[PPh2Me]I to initiate the sequential growth of either additional PLLA24[PPh2Me]I or a crystallizable blend of the latter with the block copolymer PLLA42-b-P2VP240, respectively. The epitaxial nature of the growth processes used for the creation of the 2D block comicelles was confirmed by selected area electron diffraction analysis. Crosslinking of the P2VP corona of the peripheral block in the 2D block comicelles using Pt nanoparticles followed by dissolution of the interior region in good solvent for PLLA led to the formation of novel, hollow diamond-shaped assemblies. We also demonstrate that, in contrast to the aforementioned results, seeded growth of the unsymmet-rical PLLA BCPs PLLA42-b-P2VP240 or PLLA20-b-PAGE80 alone from 2D platelets leads to the formation of diamond-fiber hybrid structures.