Application of the Diels−Alder Reaction to Polymers Bearing Furan Moieties. 2. Diels−Alder and Retro-Diels−Alder Reactions Involving Furan Rings in Some Styrene Copolymers

Abstract

Styrene copolymers containing various amounts of a novel comonomer bearing a pendant furan ring were synthesized and characterized before being submitted to Diels−Alder reactions with either a monomaleimide or a bismaleimide. Spectroscopic evidence, supported by data from model compounds, indicated that the resulting linear and cross-linked products contained extensive percentages of adduct structures formed from the furan moieties. Both types of materials were then heated in a solvent containing a large excess of 2-methylfuran in order to induce the retro-Diels−Alder and the coupling of the released maleimides with the furanic additive. The reaction proceeded as expected and the original copolymers could be recovered from the treatment. The interest in the general strategy reported here resides in the possibility of recycling cross-linked polymers by a simple thermal treatment conducted in the presence of a suitable trap.

Effect of the polymer matrix on the thermal behaviour of a furan-maleimide type adduct in the molten state

“…The peaks observed at 118°C and 119°C in Figure 2 are not present on the DSC thermograms of pure exo-adduct. They may be attributed to the melting of endo-adduct at 118°C and to the endo-exo isomerization and exo-adduct crystallization at 119°C in accordance with Gandini and al [1][2] and Mironov [22]. Peak at 156°C is attributed to exo-adduct melting as we observed change of state in sealed tube at this temperature.…”

“…The furan/maleimide couple is one of the most used diene/dienophile pairs due to the low temperature required for the DA and rDA and the high yield of products. Characterization of adducts, stereoisomers endo/exo structure, kinetic studies of DA and rDA reactions, solvent effect have been reported [1][2][3][4][5][6]. The temperature at which the rDA reactions occur depends on the specific nature of the reagents in terms of both electronic and steric effects, on the synthesis conditions and reaction mixture for a diene/dienophile pair.…”

Diels–Alder Cycloaddition‐Cycloreversion: A Powerful Combo in Materials Design

“…[5][6][7][8] polymeric materials that have excellent mechanical properties and are thermally remendable. [9] Interestingly, there are only a few examples in the literature that involve polymers appended with maleimides towards fabrication of thermoreversible materials.…”

Investigation on the thermal properties of new thermo-reversible networks based on poly(vinyl furfural) and multifunctional maleimide compounds

“…The reversibility of DA reaction is widely applied to the preparation of remarkable polymers. Thermallyreversible DA reactions have been used in numerous studies including polymer synthesis from multifunctional monomers [4,[7][8][9][10][11][12][13][14][15] or by cross-linking of functional copolymers containing maleimide or furan pendant groups [16][17][18][19][20][21][22], surface modifications [16,23], organic-inorganic polymer hybrids [24,25], reversible crosslinking polymer chains/ gels [5,16,24,26] and remendable/self-healing polymers [11,12,27]. Due to the fact that these reactions can proceed under mild conditions without a catalyst, this makes them attractive for designing covalently reversible bonds in which furan and maleimide functional groups are responsible for association and dissociation [28][29][30][31].…”