Hydrophilic Poly(meth)acrylates by Controlled Radical Branching Polymerization: Hyperbranching and Fragmentation

Area of Science:

• Polymer Chemistry
• Macromolecular Science
• Materials Science

Background:

• Hyperbranched polymers (HBPs) are crucial in various applications, but traditional synthesis methods like atom transfer radical polymerization (ATRP) often result in poor control over molecular weight distribution and branching.
• Inibramers (IBs) offer an alternative route to synthesize HBPs with controlled and uniform branching through copolymerization with vinyl monomers.

Purpose of the Study:

• To synthesize hydrophilic HB polyacrylates in water using a novel water-soluble inibramer.
• To explore the potential of this method for creating complex macromolecular structures like block copolymers and polymer-protein hybrids.
• To investigate the influence of inibramer structure on polymerization outcomes, including fragmentation.

Main Methods:

• Visible-light-mediated controlled radical branching polymerization (CRBP) using eosin Y (EY) and copper complexes.
• Copolymerization of a water-soluble inibramer, oligo(ethylene oxide) methyl ether 2-bromoacrylate (OEOBA), with hydrophilic acrylate comonomers in water.
• Synthesis of linear-hyperbranched block copolymers and hyperbranched polymer-protein hybrids (HB-PPH).
• Computational studies to analyze fragmentation mechanisms.

Main Results:

• Successfully synthesized hydrophilic HB polyacrylates with controlled molecular weights (38,000–170,000 g/mol) and degrees of branching (2%–24%).
• Demonstrated the versatility of OEOBA for creating linear-hyperbranched block copolymers and HB-PPH.
• Observed fragmentation via β-carbon C-C bond scission during copolymerization with certain monomers, influenced by IB and comonomer structure.
• Validated experimental findings through computational modeling.

Conclusions:

• Developed a water-borne CRBP system using a novel water-soluble inibramer (OEOBA) for efficient synthesis of hydrophilic HBPs.
• The study expands the available water-soluble inibramers for CRBP, enabling the creation of complex polymer architectures under environmentally friendly conditions.
• Inibramer structure critically influences polymerization pathways, including fragmentation, offering tunable synthesis strategies.