Structural reorganization of cylindrical nanoparticles triggered by polylactide stereocomplexation

Abstract

Co-crystallization of polymers with different configurations/tacticities provides access to materials with enhanced performance. The stereocomplexation of isotactic poly(L-lactide) and poly(D-lactide) has led to improved properties compared with each homochiral material. Herein, we report the preparation of stereocomplex micelles from a mixture of poly(L-lactide)-b-poly(acrylic acid) and poly(D-lactide)-b-poly(acrylic acid) diblock copolymers in water via crystallization-driven self-assembly. During the formation of these stereocomplex micelles, an unexpected morphological transition results in the formation of dense crystalline spherical micelles rather than cylinders. Furthermore, mixture of cylinders with opposite homochirality in either THF/H2O mixtures or in pure water at 65 °C leads to disassembly into stereocomplexed spherical micelles. Similarly, a transition is also observed in a related PEO-b-PLLA/PEO-b-PDLA system, demonstrating wider applicability. This new mechanism for morphological reorganization, through competitive crystallization and stereocomplexation and without the requirement for an external stimulus, allows for new opportunities in controlled release and delivery applications.

Controlling supramolecular polymerization through multicomponent self‐assembly

“…[361][362][363][364][365][366][367][368][369][370][371] Purely organic cylindrical micelles and triblock comicelles with narrow length distributions were reported by Manners, Schmalz and coworkers via CDSA using the triblock unimers PS-b-PE-b-PS and PS-b-PE-b-PMMA [where PS 5 polystyrene, PE 5 polyethylene, and PMMA 5 poly(methyl methacrylate)], driven by the crystallization of the PE block. 372 CDSA of amphiphilic diblock copolymers into cylindrical micelles of controlled length using the crystallisable core-forming blocks poly(e-caprolactone) 373 and homochiral poly(lactide) [374][375][376][377][378] were reported in water/organic solvent mixtures. The O'Reilly and Dove laboratories showed that the semicrystalline nature of the poly(L-lactide) or poly(D-lactide) was essential in obtained anisotropic micelles, since amorphous poly(DL-lactide)-based diblock copolymer unimers only produced spherical micelles in H 2 O. Well-defined cylindrical micelles (L n % 90-230 nm, -D % 1.04-1.11) were obtained for example using poly(acrylic acid) 265 -b-poly(L-lactide) 32 , by heating the dissolved amphiphilic unimers to 65 8C for 1 hour, followed by rapid cooling, suggesting that an assembly temperature above the T g of poly(lactide) facilitates crystallization of the core block during the assembly process.…”

Two-dimensional assemblies from crystallizable homopolymers with charged termini

“…19,38,39 Two homopolymers with phosphonium groups at a chain terminus were prepared, PLLA24 Fig. 26).…”

Monodisperse Cylindrical Micelles and Block Comicelles of Controlled Length in Aqueous Media

“…29 In this context, BCPs with crystallizable poly(ferrocenyldimethylsilane) (PFS), 30 polycaprolactone, 31,32 poly(L-lactic acid), 33,34 polyethylene, 35 polyacrylonitrile 36 , polythiophene, 37,38 and polyselenophene 39 core-forming blocks have been reported to form polydisperse cylindrical micelles. By optimizing the self-assembly conditions, researchers have been able to achieve some control over the length of cylindrical micelles formed by a variety of poly(L-lactic acid)- [40][41][42][43][44] and polycaprolactone-based 45 BCPs in aqueous media. In addition, post-self-assembly methods such as fragmentation during extrusion have also been employed to reduce the length of cylindrical micelles.…”