Jingkai Nie,Hang Yin,Ruyue Cao,Changyuan Huang,Xiang Luo,Jun Ji
This paper developed a method for preparing ultrasound-responsive microgels based on reversible addition fragmentation chain transfer-hetero Diels–Alder (RAFT-HAD) dynamic covalent bonding. First, a styrene cross-linked network was successfully prepared by a Diels–Alder (DA) reaction between phosphoryl dithioester and furan using double-ended diethoxyphosphoryl dithiocarbonate (BDEPDF) for RAFT reagent-mediated styrene (St) polymerization, with a double-ended dienophile linker and copolymer of furfuryl methacrylate (FMA) and St as the dienophile. Subsequently, the microgel system was constructed by the HDA reaction between phosphoryl disulfide and furan groups using the copolymer of polyethylene glycol monomethyl ether acrylate (OEGMA) and FMA as the dienophore building block and hydrophilic segment and the polystyrene pro-dienophile linker as the cross-linker and hydrophobic segment. The number of furans in the dienophile chain and the length of the dienophile linker were regulated by RAFT polymerization to investigate the effects of the single-molecule chain functional group degree, furan/dithioester ratio, and hydrophobic cross-linker length on the microgel system. The prepared microgels can achieve the reversible transformation of materials under force responsiveness, and their preparation steps are simple and adaptive to various potential applications in biomedical materials and adaptive electrical materials.
This study introduces a novel approach combining reversible addition–fragmentation chain transfer (RAFT) polymerization and hetero-Diels–Alder (HDA) reactions to efficiently synthesize hyperbranched polymers (HBPs) with controlled topology. The traditional ABn monomer methods for creating HBPs face limitations due to random polymerization and the risk of gelation. By optimizing the ABn system into an ABx macromonomer framework, this new RAFT–HDA method enables controlled polymerization, reducing intramolecular cyclization and topological defects and broadening the range of possible polymer architectures. Additionally, more readily available and widely used novel dienes and dienophiles have been identified for the HDA reaction. The versatility of this approach was demonstrated by synthesizing a variety of HBPs with different branching degrees and molecular weights, which were thoroughly characterized by NMR, FTIR, GPC, and DLS techniques. This study provides a robust and efficient pathway for synthesizing complex polymer structures, demonstrating that the RAFT–HDA strategy enables the production of well-defined hyperbranched polymers with significant potential for applications in nanomaterials, biomedicine, and advanced functional materials.
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