Synthesis of Novel Star Polymers with Vinyl-Functionalized Hyperbranched Core via “Arm-First” Strategy

Exploiting the Monomer-Feeding Mechanism of RAFT Emulsion Polymerization for Polymerization-Induced Self-Assembly of Asymmetric Divinyl Monomers

We exploited the monomer-feeding mechanism of reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization to achieve the successful polymerization-induced self-assembly (PISA) of asymmetric divinyl monomers. Colloidally stable cross-linked block copolymer nanoparticles with various morphologies, such as vesicles, were directly prepared at high solids. Morphologies of the cross-linked block copolymer nanoparticles could be controlled by varying the monomer concentration, degree of polymerization (DP) of the core-forming block, and length of the macro-RAFT agent. X-ray photoelectron spectroscopy (XPS) characterization confirmed the presence of unreacted vinyl groups within the obtained block copolymer nanoparticles, providing a landscape for further functionalization via thiol-ene chemistry. Finally, the obtained block copolymer nanoparticles were employed as additives to tune the mechanical properties of hydrogels. We expect that this study not only offers considerable opportunities for the preparation of well-defined cross-linked block copolymer nanoparticles, but also provides important insights into the controlled polymerization of multivinyl monomers.

“Core-first” approach for the synthesis of star-shaped polyisoprenes with a branched core and isoprene catalyzed by half-sandwich scandium complexes

Star-shaped polyisoprenes were synthesized by copolymerization of isoprene and branched homopolymer of dimethyl-di-2,4-pentadienyl-(E, E)-silane through “Core-first” approach catalyzed by half-sandwich scandium complex.

Regioselective, stereoselective, and living polymerization of divinyl pyridine monomers using rare earth catalysts

The first regioselective, stereoselective, and living polymerization of divinyl pyridine monomers, mediated by simple rare earth catalysts, is reported.

Star Polymers

Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

In Situ Cross-Linking of Vesicles in Polymerization-Induced Self-Assembly

In situ cross-linking of nano-objects with controllable morphologies in polymerization-induced self-assembly (PISA) has been a challenge because cross-linking lowers chain mobility and hence inhibits morphology transition. Herein, we propose a novel strategy that allows in situ cross-linking of vesicles in PISA in an aqueous dispersion polymerization formulation. This is realized by utilizing an asymmetric cross-linker bearing two vinyl groups of differing reactivities such that cross-linking is delayed to the late stage of polymerization when morphology transition has completed. Cross-linked vesicles with varying degrees (1-5 mol %) of cross-links were prepared, and their resistance to solvent dissolution and surfactant disruption was investigated. It was found that vesicles with ≥2 mol % cross-links were able to retain their structural integrity and colloidal stability when dispersed in DMF or in the presence of 1% of an anionic surfactant sodium dodecyl sulfate.

Controlled Divinyl Monomer Polymerization Mediated by Lewis Pairs: A Powerful Synthetic Strategy for Functional Polymers

Lewis pair cooperation provides a facile approach for polymerizing dissymmetric divinyl polar monomers such as 4-vinylbenzyl methacrylate in excellent regioselectivity and high reactivity at mild conditions, affording soluble polymers bearing pendant active vinyl groups with high molecular weight (up to 6.4 × 10⁵ g/mol) and narrow polydispersity (PDI < 1.5). ESI-TOF MS study demonstrated that the polymerization process only concerned the methacrylic double bond and selectively remained the pendant allylic or styrene C═C bond.

Efficient and versatile synthesis of star polymers in water and their use as emulsifiers

Core cross-linked star polymers of low polydispersity were efficiently prepared in high yield by RAFT-mediated emulsion and dispersion polymerizations in water at high solid content. These star polymers were demonstrated to be effective emulsifiers, and the emulsion was successfully used as template to fabricate polymer particles.