Synthesis of Macrocyclic Polymers Formed via Intramolecular Radical Trap-Assisted Atom Transfer Radical Coupling.

Area of Science:

• Polymer Chemistry
• Organic Synthesis

Background:

• Linear polymers with specific end-group functionalities are crucial for advanced material design.
• Intramolecular cyclization is a challenging but valuable method for creating well-defined polymer architectures.

Purpose of the Study:

• To develop an efficient method for synthesizing cyclic polystyrene (PSt) with alkoxyamine functionality.
• To investigate the use of radical trap-assisted intramolecular atom transfer radical coupling (RTA-ATRC) for polymer cyclization.

Main Methods:

• Synthesis of linear α,ω-dibrominated polystyrene via atom transfer radical polymerization (ATRP).
• Intramolecular radical coupling under pseudodilute conditions using 2-methyl-2-nitrosopropane (MNP) as a radical trap.
• Characterization of cyclic polymers using gel permeation chromatography (GPC) and liquid chromatography-mass spectrometry (LC-MS).

Main Results:

• Achieved cyclic polymer yields greater than 90% with narrow polydispersity (⟨G⟩ values of 0.8-0.9).
• Confirmed cyclic structure and alkoxyamine incorporation via LC-MS.
• Demonstrated thermal-induced ring-opening, reverting to the original apparent molecular weight.

Conclusions:

• RTA-ATRC is a highly effective method for producing alkoxyamine-functionalized cyclic polystyrene.
• The incorporated alkoxyamine group allows for controlled thermal-induced ring-opening.
• This methodology offers a robust route to well-defined cyclic polymers for potential applications.