Controlling the Self-Assembly of Binary Copolymer Mixtures in Solution through Molecular Architecture

Multicore Assemblies from Three-Component Linear Homo-Copolymer Systems: A Coarse-Grained Modeling Study

Multicore polymer micelles and aggregates are assemblies that contain several cores. The dual-length-scale compartmentalized solvophobic–solvophilic molecular environment makes them useful for, e.g., advanced drug delivery, high-precision synthesis platforms, confined catalysis, and sensor device applications. However, designing and regulating polymer systems that self-assemble to such morphologies remains a challenge. Using dissipative particle dynamics (DPD) simulations, we demonstrate how simple, three-component linear polymer systems consisting of free solvophilic and solvophobic homopolymers, and di-block copolymers, can self-assemble in solution to form well-defined multicore assemblies. We examine the polymer property range over which multicore assemblies can be expected and how the assemblies can be tuned both in terms of their morphology and structure. For a fixed degree of polymerization, a certain level of hydrophobicity is required for the solvophobic component to lead to formation of multicore assemblies. Additionally, the transition from single-core to multicore requires a relatively high solvophobicity difference between the solvophilic and solvophobic polymer components. Furthermore, if the solvophilic polymer is replaced by a solvophobic species, well-defined multicore–multicompartment aggregates can be obtained. The findings provide guidelines for multicore assemblies’ formation from simple three-component systems and how to control polymer particle morphology and structure.

Morphology Under Control: Engineering Biodegradable Stomatocytes

Biodegradable nanoarchitectures, with well-defined morphological features, are of great importance for nanomedical research; however, understanding (and thereby engineering) their formation is a substantial challenge. Herein, we uncover the supramolecular potential of PEG-PDLLA copolymers by exploring the physicochemical determinants that result in the transformation of spherical polymersomes into stomatocytes. To this end, we have engineered blended polymersomes (comprising copolymers with varying lengths of PEG), which undergo solvent-dependent reorganization inducing negative spontaneous membrane curvature. Under conditions of anisotropic solvent composition across the PDLLA membrane, facilitated by the dialysis methodology, we demonstrate osmotically induced stomatocyte formation as a consequence of changes in PEG solvation, inducing negative spontaneous membrane curvature. Controlled formation of unprecedented, biodegradable stomatocytes represents the unification of supramolecular engineering with the theoretical understanding of shape transformation phenomena.

Compact Vesicles Self-Assembled from Binary Graft Copolymers with High Hydrophilic Fraction for Potential Drug/Protein Delivery

Hollow vesicles self-assembled from amphiphilic copolymers are of great interest in biomedicine field as drug and protein carriers. Efficient preparation of polymeric vesicles with high stability in vivo is highly desirable. Herein, a novel cooperative self-assembly of two graft copolymers (GCPs) with reversed hydrophilic-hydrophobic segments is investigated to achieve morphology control for biomedical application. Interestingly, nanosized vesicles are obtained for the binary system with relatively high hydrophilic fraction (f_hydrophilic, ∼60%), contrary to what is found in its single-component counterpart. The cooperative self-assembly endowed the hybrid vesicles with excellent resistance to protein adsorption, prolonged blood circulation time, as well as low leakage of hydrophilic drugs/proteins. Furthermore, the biological activity of the protein is well preserved inside the cooperative vesicles, making it a promising candidate as the protein carrier.

Robust formation of biodegradable polymersomes by direct hydration

A mild, robust and fast method to form nano-sized biodegradable polymersomes is described.

Modification of block copolymer vesicles: what will happen when AB diblock copolymer is block-extended to an ABC triblock terpolymer?

The PEG-b-PS diblock copolymer vesicles were converted into the membrane-compartmentalized vesicles of the PEG-b-PS-b-P4VP triblock terpolymer through seeded RAFT polymerization.

Crystallinity-driven morphological ripening processes for poly(ethylene oxide)-block-polycaprolactone micelles in water

A set of morphological transformations induced by core crystallization within spherical micelle-like aggregates of poly(ethylene oxide)-block-polycaprolactone (PEO-b-PCL) is described in the present article. The initial self-assembly step, in which individual copolymer chains associate to form the spheres, can be performed reproducibly; the stability of these spheres, however, seems to be limited, as both transmission electron microscopy and light scattering data suggest that the primary spheres transform slowly into elongated rod-like or ribbon-like aggregates when suspended in deionized water at room temperature. Although the sphere-to-rod transition takes place typically over a time scale of several days, the formation of individual rods from spheres is very rapid, as evidenced by the progressive increase in the number of long rods and the conspicuous absence of short rods.

Nanoparticle-to-vesicle and nanoparticle-to-toroid transitions of pH-sensitive ABC triblock copolymers by in-to-out switch

An efficient way to achieve nanoparticle-to-vesicle transition of ABC triblock copolymers by in-to-out switch of the pH-sensitive core-forming block is described.