Macrocyclic poly(methyl acrylate) and macrocyclic poly(methyl acrylate-block-styrene) synthesized by radical trap-assisted atom transfer radical coupling. (26th June 2015)

• Record Type: Journal Article
• Authors: Blackburn, Scott C.; Myers, Kenneth D.; Tillman, Eric S.
• Is Part Of: Polymer. Volume 68(2015)
• Page Start: 284
• Page End: 292
• Publication Date: 2015-06-26
• Subjects: Atom transfer radical coupling -- Atom transfer radical polymerization -- Macrocycle -- Polyacrylate; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2015.05.021
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Dibrominated poly(methyl acrylate) (BrPMABr) was prepared by atom transfer radical polymerization (ATRP), and this unpurified reaction mixture was used directly in a radical trap-assisted atom transfer radical coupling (RTA-ATRC) reaction to achieve cyclic PMA by intramolecular chain-end coupling. When the polymerization-to-cyclization crossover was performed as a one pot-two step sequence simply by the addition of the radical trap 2-methyl-2-nitrosopropane (MNP) and increased amounts of ligand-catalyst complex, cyclic PMA could be formed in yields up to 65% by adjusting the total volume and reactant ratios during the intramolecular RTA-ATRC, based on gel permeation chromatography (GPC) analysis. In analogous intramolecular ATRC trials lacking the radical trap, cyclization was not successful and instead chain extension by continuation of ATRP was observed. When the ATRP reaction mixture containing the BrPMABr precursor was added drop-wise into a redox active solution containing MNP, yields of cyclic polymer were increased up to 85%. The effect of the ligand was studied, with the highest amounts of cyclic product obtained in intramolecular RTA-ATRC reactions using tris[2-(dimethylamino)ethyl]amine (Me6 TREN) as the ligand. Cyclic diblock copolymers were also prepared by this method, using telechelic poly(methyl acrylate- block -styrene- block -methyl acrylate) (PMA-b-PS-b-PMA) linear precursors prepared by sequential ATRP reactions. Graphical abstract: Highlights: Cyclic PMA was produced by the intramolecular RTA-ATRC of dibrominated PMA. Cyclic diblock copolymers were obtained from linear BAB-type triblocks. Cyclic polymers were verified by gel permeation chromatography and mass spectrometry. Polymerization-to-cyclization was performed without purification of linear precursors.