Post-polymerization modification of polymeric active esters towards TEMPO containing polymers: A systematic study

• Published in: European polymer journal Vol. 130; p. 109660
• Main Authors: Xue, Wenwen, Mutlu, Hatice, Theato, Patrick
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 05.05.2020; Elsevier BV
• Subjects: Acrylamide; Batteries; Carboxylic acids; Catalysts; Chemical reactions; Energy storage; Esters; Hydrolysis; Nucleophiles; Oxidation; Polymerization; Polymers; Prepolymers; Reaction time; Steric hindrance; Storage batteries; Transesterification; Trimethylamine
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2020.109660

[Display omitted] •For the first time, a systematic study was performed on the post-polymerization modification of polymeric active esters towards distinct TEMPO containing polymers with varying backbone composition.•The influence of side reactions (such as hydrolysis) on the redox reaction of TEMPO containing polymers was explored.•The battery performance of polymer with the highest TEMPO content was investigated exhibits a 12–22 mAh/g higher specific capacity compared to PTMA synthesized by conventional oxidation method when running at 5 C for 500 cycles. Organic radical batteries (ORB) are a novel promising class for energy storage, particularly featuring a fast charging capability and extraordinary cycle life. The representative polymer, i.e. poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA), is usually synthesized by a post-polymerization oxidation method. As an alternate strategy for developing TEMPO-containing polymers, we focused on the post-polymerization modification of poly(pentafluorophenyl acrylate) and poly(pentafluorophenyl methacrylate) with three different TEMPO nucleophiles by transesterification or amidation reactions. Optimizing the conditions of the post-polymerization functionalization reaction by varying different parameters, such as the type of nucleophile, catalyst and solvent, the feeding ratios of catalysts and nucleophiles, along with reaction time and temperatures, resulted in structurally distinct TEMPO containing polymers with varying backbone composition. Intriguingly, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) revealed the highest degree functionalization with TEMPO (96.2%) within 3 hrs. under considerably mild conditions, while poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methylmethacrylamide) exhibited the lowest TEMPO content owing to the steric hindrance from methyl group on both the methacrylate chain and the TEMPO derivative. All other four TEMPO containing polymers had a radical content similar to PTMA (66.6%) synthesized by the post-oxidation methodology. Noteworthy, compared to TEA (trimethylamine), DMAP (4-dimethylaminopyridine) facilitated an efficient ester bond cleavage independent of the polymer precursor, thus, side reactions such as hydrolysis were increased. Though hydrolysis side reaction occurred, the resulting carboxylic acid group was proven to accelerate ion transfer in a certain way during the redox process. Furthermore, due to the higher TEMPO content, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) exhibited a 12–22 mAh/g higher specific capacity compared to the PTMA-oxidation when running at 5C for 500 cycles.