Synthesis, characterization and the paramagnetic properties of bottle-brush copolymers with shielding TEMPO radicals. Issue 45 (10th November 2017)

• Record Type: Journal Article
• Authors: Wang, Jian; Wu, Zhigang; Shen, Hongying; Wang, Guowei
• Is Part Of: Polymer chemistry. Volume 8:Issue 45(2017)
• Page Start: 7044
• Page End: 7053
• Publication Date: 2017-11-10
• Subjects: Polymers -- Periodicals; Macromolecules -- Periodicals; Polymerization -- Periodicals; 547.705
• DOI: 10.1039/c7py01683b
• Languages: English
• ISSNs: 1759-9954

Abstract

Abstract : Bottle-brush copolymers PHEMA- g -[(PAA- g -TEMPO)- b -PMA] and PHEMA- g -(PAA- g -TEMPO) with shielding TEMPO radicals were synthesized. The paramagnetic properties in bulk and solution were studied, and the results confirmed that the presence of the outer segment played an important role on the EPR spectra of copolymers. Abstract : Bottle-brush copolymers poly(2-hydroxyethyl methacrylate)(PHEMA)- g -{[(poly(acrylic acid)- g -2, 2, 6, 6-tetramethylpiperidine-1-oxyl)]- b -poly(methyl acrylate)} (PHEMA- g -[(PAA- g -TEMPO)- b -PMA]) and PHEMA- g -(PAA- g -TEMPO) with shielding 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) radicals were synthesized, and their paramagnetic properties were compared in bulk and solution, respectively. Firstly, using a "grafting from" strategy, the atom transfer radical polymerization (ATRP) of tert -butylacrylate ( t BA) permitted the successful synthesis of the bottle-brush copolymer PHEMA- g -P t BA from the macro-initiator poly[2-(2-bromoisobutyryloxy)ethyl methacrylate] (PBiBEMA) with a high density of initiating sites. Subsequently, following a second "grafting from" strategy and the ATRP of methyl acrylate (MA), the bottle-brush copolymer PHEMA- g -(P t BA- b -PMA) was further produced by employing PHEMA- g -P t BA as the macro-initiator. The poly(acrylic acid) (PAA) segment generated by the selective hydrolysis of the P t BA segment was used to introduce TEMPO radicals through the reaction between carboxyl groups on PAA and oxirane group on glycidoloxy-2, 2, 6, 6-tetramethyl piperidine-1-oxyl (GTEMPO). With the shielding by the outer PMA segment in PHEMA- g -[(PAA- g -TEMPO)- b -PMA], superfine information of inner TEMPO radicals in the electron paramagnetic resonance (EPR) spectrum could be well discriminated. However, the PHEMA- g -(PAA- g -TEMPO) without any shielding showed a broad EPR spectrum, which was in accordance with a characteristic EPR spectrum of a polyradical polymer due to the strong interactions between radicals.