Polymerization-Induced Self-Assembly of Comb-like Amphiphilic Copolymers into Onion-like Vesicles

Regulating the Chiroptical Expression of Aggregated Solvophobic Core by Solvophilic Segments

The investigation of chiral supramolecular stacking is of essential significance for the understanding of the origin of homochirality in nature. Unlike structurally well-defined amphiphilic liposomes, it remains unclear whether the solvophilic segments of the amphiphilic block copolymer play a decisive role in the construction of asymmetric superstructures. Herein, insights are presented into the stacking patterns and morphological regulation in azobenzene-containing block copolymer assemblies solely by modulating the solvophilic chain length. The solvophilic poly(methacrylic acid) (PMAA) segments of different molecular weights could cause multi-mode chirality inversions involving stacking transitions between intra-chain π-π stacking, inter-chain H- and J-aggregation. Furthermore, the length of the solvophilic PMAA also affects the morphology of the chiral supramolecular assemblies; rice grain-like micelles, worms, nanofibers, floccules, and lamellae can be prepared at different solvophilic-solvophobic balance. The comprehensive mechanism is collectively revealed by utilizing various measurement methods, such as including circular dichroism (CD), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD). This study highlights the critical importance of fully dissolved solvophilic segments for the chiroptical regulation of the aggregated core, providing new insights into the arrangement of chiral supramolecular structures in polymer systems.

Modular addition strategy-regulated polymerization-induced self-assembly: an in silico experiment

We propose a modular addition strategy-regulated polymerization-induced self-assembly (PISA) system to effectively control the reaction kinetics and self-assembly morphologies. We validated this strategy by performing in silico experiments on a well-established PISA system. Two categories of modular addition strategies, i.e., the multistep addition strategy and the constant rate addition strategy, were investigated. Results showed that the modular addition operation of macromolecular chain transfer agents (macro-CTAs) effectively regulated the width of the molecular weight distribution for the hydrophobic PSt block, which further led to an assembly of vesicle structures with irregular aspherical cavities. Besides, we found a new transition pathway for the formation of vesicles, which involved generation of small vesicles in the early stage followed by a gradual growth in the intermediate and late stages. In the constant rate addition strategy, with the increase in the addition rate of macro-CTA, we found that the morphology basically tended to change from a micellar structure to a vesicle structure. This study holds potential to inspire future work toward the improvement of experimental techniques in PISA-relevant systems.

Nano onions based on an amphiphilic Au3(pyrazolate)3 complex

Multilayer vesicles with an onion-like architecture can form by self-assembly of organic amphiphiles such as dendrimers, small-molecule surfactants, and block copolymers. Thus far, there are limited reports about multilayer vesicles based on coordination compounds. Herein, we show that nano onions are obtained by aggregation of an amphiphilic Au3(pyrazolate)3 complex in aqueous solution. The nanostructures were characterized by cryogenic and transition electron microscopy, dynamic light scattering, and energy-dispersive X-ray analysis. Control experiments with analogous Ag(I) and Cu(I) complexes revealed the importance of Au(I) for the formation of well-defined nano onions. A structurally related Au(I) complex without solubilizing polyethylene glycol side chains was analyzed by single-crystal X-ray diffraction. In the solid state, columns of offset, π-stacked Au3(pyrazolate)3 complexes are observed, but short intermolecular Au⋯Au contacts were not found. Molecular dynamics simulations provided further insights into the aggregation process in aqueous solution, supporting the formation of nano-onion structures through lateral interactions between stacked complexes.

Self-assembly of amphiphilic asymmetric comb-like copolymers with responsive rigid side chains

Amphiphilic asymmetric comb-like copolymers (AACCs) exhibit distinct self-assembly behaviours due to their unique architecture. However, the synthetic difficulties of well-defined AACCs have prohibited a systematic understanding of the architecture-morphology relationship. In this work, we conducted dissipative particle dynamics simulations to investigate the self-assembly behaviours of AACCs with responsive rigid side chains in selective solvents. The effects of side chain length, number of branches, and spacers on the morphology of aggregates were investigated by mapping out morphology diagrams. Besides, the numbers and surface areas of aggregates clearly depicted the morphological transitions during the self-assembly process. Moreover, the rod-to-coil conformation transitions were simulated to explore the stimuli-responsive behaviour of the AACCs with responsive rigid side chains by adjusting the bond angle parameter of the rigid chains. The results indicated that without the support of the rigid chains, the assembly structure collapsed, leading to the tube-to-channelized micelles and one-compartment-to-multicompartment vesicle morphology transformations. The simulation results are consistent with earlier experimental results, which can provide theoretical guidance for assembly toward desired nanostructures.

A Simple Stochastic Reaction Model for Heterogeneous Polymerizations

The stochastic reaction model (SRM) treats polymerization as a pure probability‐based issue, which is widely applied to simulate various polymerization processes. However, in many studies, active centers were assumed to react with the same probability, which cannot reflect the heterogeneous reaction microenvironment in heterogeneous polymerizations. Recently, we have proposed a simple SRM, in which the reaction probability of an active center is directly determined by the local reaction microenvironment. In this paper, we compared this simple SRM with other SRMs by examining living polymerizations with randomly dispersed and spatially localized initiators. The results confirmed that the reaction microenvironment plays an important role in heterogeneous polymerizations. This simple SRM provides a good choice to simulate various polymerizations.

Self-Assembled Polymeric Materials: Design, Morphology, and Functional-Oriented Applications

This Review focuses on the current research advances of the synthesis of various amphiphilic block copolymers (ABCs), such as conventional ABCs and newly-presented polyprodrug amphiphiles (PPAs), and the development of corresponding self-assemblies in selective solvents driven by the intermolecular interactions, like noncovalent hydrophobic interactions, π-π interactions, and hydrogen bonds, between ABCs or preformed small polymeric nanoparticles. The design of these assemblies is systematically introduced, and the diverse examples concerning the unique assembly structures along with the fast development of their exclusive properties and various applications in different fields were discussed. Possible perspectives on the existential challenges and glorious future were elucidated finally. We hope this review will provide a convenient way for readers to motivate more evolutional innovative concepts and methods to design next generation of novel polymeric nanoassemblies, and fill the gap between material design and practical applications. This article is protected by copyright. All rights reserved.