Asymmetric Colloidal Particles Fabricated by Polymerization-Induced Surface Self-Assembly Approach

Abstract

In the past decades, the synthesis of asymmetric colloidal particles has been of wide concern in material science because of their anisotropic morphologies and unique properties. However, the synthesis of the asymmetric particles with controllable anisotropy still remains a big challenge because of the lack of effective methods. In this research, polymerization-induced surface self-assembly (PISSA) approach was demonstrated to be an effective method in the synthesis of colloidal particles with tunable asymmetric core–shell structures. Reversible addition–fragmentation chain transfer agents were covalently anchored onto the surfaces of silica particles and coupled onto the ends of methoxy polyethylene glycol (PEG) chains, leading to the synthesis of CTA-modified silica particles (SiO2-CTA) and PEG macro-CTA agents (PEG-CTA), respectively. PISSA process was conducted by using SiO2-CTA and PEG-CTA as co-RAFT agents in RAFT dispersion polymerization of styrene. In the RAFT polymerizations, polymer layers with PS nodules were formed on the surfaces of SiO2 particles. It was demonstrated that the formation of the nodules was related to the production of the PS homopolymer in the PISSA process. In order to control the asymmetric surface structures, RAFT dispersion polymerizations of styrene with added “free” RAFT agents were performed, and it turned out that the eccentrically positioned core–shell structures with silica cores and polymer layers were prepared. The colloidal particles experience morphology changes from surface nodules to snowman-like structures and finally to asymmetric spherical structures, depending on the monomer conversion and the feeding ratio of the co-RAFT agents. Kinetics studies were performed to investigate the mechanism of the formation of the asymmetric particles. After etching the silica cores with HF solution, asymmetric hollow capsules were fabricated.

Organic–inorganic hybrid nanomaterials prepared via polymerization-induced self-assembly: recent developments and future opportunities

“…The morphologies of organic-inorganic hybrid nanocomposites can be controlled by changing the molecular weights of the solvophilic block and the solvophobic block. Using a similar strategy, the same group 177 performed PISA mediated by a mixture of a linear macro-CTA dissolved in the reaction medium and CTA-grafted silica nanoparticles. In this case, asymmetric organic-organic hybrid nanoparticles with tunable anisotropy were formed.…”

Polymer brush-based nanostructures: from surface self-assembly to surface co-assembly

“…Recently, Hou and coworkers reported the RAFT dispersion polymerization of styrene using This journal is © The Royal Society of Chemistry 2022 three different chain transfer reagents, 4-cyano-4-(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid (CDTPA), PEG-CTA and SiO 2 -CTA. 218 As shown in Fig. 22, core-shell colloidal particles with SiO 2 in the cores and the polymer assembly in the shells were prepared by PISSA.…”

Homopolymer-Assisted Fusions of Polymer Brushes and Block Copolymer Vesicles

“…In a previous research we found that asymmetric particles with silica cores and polymer layers could be synthesized by a polymerization-induced surface selfassembly (PISSA) approach, and PS homopolymer chains produced in the approach played a key role in the formation of the asymmetric surface structures. 34 Inspired by the research, the effect of the added homopolymer on the surface coassembly of polymer brushes and "free" BCP chains was investigated. Herein, surface coassembly of poly(ethylene glycol)-block-polystyrene (PEG-b-PS) and PS brushes in the presence of PS homopolymer was studied, and we found that the added homopolymer chains were able to induce the fusions of polymer brushes and BCP vesicles, and large compound hybrid structures with multiple cavities on the surfaces were produced.…”

“…A variety of surface nanostructures, including spherical and worm-like s-micelles and layered surface structures, are fabricated by the surface coassembly approach. In a previous research we found that asymmetric particles with silica cores and polymer layers could be synthesized by a polymerization-induced surface self-assembly (PISSA) approach, and PS homopolymer chains produced in the approach played a key role in the formation of the asymmetric surface structures . Inspired by the research, the effect of the added homopolymer on the surface coassembly of polymer brushes and “free” BCP chains was investigated.…”