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 a 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 co-micelles 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 co-micelles was confirmed by selected area electron diffraction analysis. Cross-linking of the P2VP corona of the peripheral block in the 2D block co-micelles 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 unsymmetrical PLLA BCPs PLLA42-b-P2VP240 or PLLA20-b-PAGE80 alone from 2D platelets leads to the formation of diamond-fiber hybrid structures.