Thermally reversible polymer linkages. 3. Covalently crosslinked poly(azlactone)

Abstract

Research on the azlactone-phenol reaction has been extended to cross-linking chemistry. Poly-(2-vinyl 4,4-dimethyl-2-oxazolin-5-one) was used to synthesize three-dimensional networks using bisphenol cross-linkers. Among the bisphenols considered, only bisphenols containing electron-withdrawing groups at the site para to the phenol hydroxyls cross-link the polymer. The bisphenol 4,4'-(perfluorobutanediyl-1,4disulfonyl)diphenol was also found to facilitate the reverse reaction in high-boiling solvents, re-forming linear polymer and bisphenol at temperatures below the degradation temperature of the linear polymer. These networks undergo up to 20 or more cycles of cross-linking-de-cross-linking both inside and outside of the drybox.

Covalent Adaptable Networks (CANs): A Unique Paradigm in Cross-Linked Polymers

“…Nucleophilic addition reaction involving ring opening have also received attention as thermal CANs. Linear polymers with either pendant maleic acid23, 24 or azlactone25 functional groups crosslinked by a bis-alcohol have been shown as a viable thermoreversible crosslinking reaction; however, these materials have limited reversibility owing to various side reactions 26. Carbene dimerization is another candidate reaction for the basis of a thermal CAN (reaction 2 in Figure 2).…”

Study of the Diels–Alder and retro-Diels–Alder reaction between furan derivatives and maleimide for the creation of new materials

“…For this study, the temperature, which is the easier way for industrialization, has been chosen. Systems such as the urethane group, 4 nitroso group, 5 ester group, 6 ionene complex, [7][8][9][10] azlactone-phenol adduct 11,12 and, lastly, the Diels-Alder adduct [13][14][15][16][17][18] allow the formation of reversible covalent bonds under high temperature conditions. The Diels-Alder system was chosen for this project, in spite of existing studies, 14,[19][20][21] because this is the most famous and the easier system.…”

Improved “cure on demand” of aromatic bismaleimide with thiol triggered by retro-Diels-Alder reaction

“…Temperature is the easier stimulus to break organic bonds between two molecules. Many well-known systems are capable of forming reversible covalent bonds at different temperatures [4][5][6][7][8][9][10][11][12][13][14][15][16]. However, the thermal reversibility can be used (and is used to a low extend) for other aims, such as the recycling of polymers or to protect reversible functional groups in order to control polymerization or crosslinking.…”