Hierarchical Self-Assembly of Poly(d-glucose carbonate) Amphiphilic Block Copolymers in Mixed Solvents

Abstract

We report the fibril formation of poly­(d-glucose carbonate) (PGC)-based amphiphilic diblock copolymers using solution assembly. Unlike conventional cylindrical micelles constructed from amphiphilic block copolymers (BCPs) with coil-like blocks, the assembled PGC fibrils exhibit thin, ribbon-like features due to significant stiffness and hydrophobicity of the PGC BCP backbone that result in a unique polymer chain packing. A tetrahydrofuran/H2O solvent mixture was used to create a solvent quality gradient during which a hierarchical assembly pathway was observed with fibril precursor nanoparticles that linked together into fibrils. These initial precursors were soft, patchy nanoparticles caused by the phase-segregated hydrophilic block of the PGC diblock copolymer. With aging, the patchy nanoparticles underwent unidirectional attachment through hydrophobic association to transform into uniform fibril structures. Transmission electron microscopy, interpretation of the small-angle neutron scattering measurements fit with analytical models, and genetic algorithm-based reverse engineering of structure confirmed the presence of initial particle precursors, intermediate stages during growth, and the fully matured fibrils. The results suggest that unconventional backbone chemistry-based molecules reveal unique effects of chain stiffness and hydrophobicity on block copolymer solution assembly when using glucose-based polycarbonates.

Supramolecular Interactions and Morphology of Self-Assembling Peptide Amphiphile Nanostructures

“…As fibrils grow wider, β-sheets further from the center of the assemblies become increasingly deformed from their ideal configuration, limiting the lateral growth of fibrils. Similar morphologies have been observed in a wide array of self-assembling supramolecular systems, such as chiral surfactants which form a polydisperse mixture of twisted ribbonlike structures, − supramolecular aggregates of ethylene glycol, and glycerol with aliphatic tails that assemble into paired cylinders or twisted double helices, cholesterol assemble into helical ribbons in cellular environments, aromatic amino acids that aggregate into high rigidity twisted ribbons, , and biological sugar-based block copolymers or coil–brush block polymers which form hierarchical twisted nanoassemblies. , …”

“…Similar morphologies have been observed in a wide array of self-assembling supramolecular systems, such as chiral surfactants which form a polydisperse mixture of twisted ribbonlike structures, 29−31 supramolecular aggregates of ethylene glycol, and glycerol with aliphatic tails that assemble into paired cylinders or twisted double helices, 32 cholesterol assemble into helical ribbons in cellular environments, 33 aromatic amino acids that aggregate into high rigidity twisted ribbons, 34,35 and biological sugar-based block copolymers or coil−brush block polymers which form hierarchical twisted nanoassemblies. 36,37 The morphology of structures formed by different PAs has been explored empirically; however, it remains an open challenge to understand the mechanistic relation between the peptide sequence in a PA and the resulting nanostructure. 38 In this work, we systematically explore the self-assembly of a set of PA molecules previously synthesized in the authors' laboratory, to investigate the role of peptide sequence and electrostatics on supramolecular morphology.…”

Computational Reverse-Engineering Analysis of Scattering Experiments (CREASE) on Amphiphilic Block Polymer Solutions: Cylindrical and Fibrillar Assembly

“…All micelle shapes in this study have a core domain made of the solvophobic blocks of the BCPs surrounded by a corona domain made of solvophilic blocks of the BCP. Even though this paper is focused on these specific morphologies, we note that the method section is written in a manner that one could extend to other morphologies and shapes such as supramolecular assemblies, vesicles, onion-like layer-by-layer arrangement, or nontraditional core–corona BCP packing. − …”

“…The I exp ( q ) values generated from in silico experiments mimic realistic BCP solutions, whereas the I exp ( q ) values generated from the placement of scatterers in set dimensions serve as mathematical tests for CREASE. For studies where we have used CREASE on I exp ( q ) from real scattering experiments, we direct the reader to our recent publications. , …”

Alginate-Based Amphiphilic Block Copolymers as a Drug Codelivery Platform

“…Huang et al also developed docetaxel-loaded nanoparticles using hyaluronic acid/poly­( d , l -lactide- co -glycolide) block copolymers that targeted CD44 receptors in breast cancer . Synthetic glucose-based amphiphilic block copolymers developed by Wooley and co-workers have shown self-assembly into spherical, cylindrical, or thin, ribbon-like nanostructures depending on their compositions and domain sizes. − …”