Polyurethanes based on thermoreversible networks designed by Diels-Alder reaction

Abstract

Polyurethanes appeared as a Bayer's response to the successful development of high molecular weight polyamides by E.I. Dupont, given the competition between the two companies. The need for PUs steadily increased ever since then, because of its high abrasion, chemical resistance, flexibility, and good mechanical property [1]. Nowadays they are considered one of the most versatile polymeric materials class since they can be used in many forms and in a large number of applications including elastomers [2][3][4][5], flexible and rigid foams [6][7][8], biomedical applications [9][10][11], adhesives and coatings [12][13][14], polymers for electronics [15], etc. The reaction between diisocyanates or multiisocyanates and di-or polyols generates polyurethanes with different molecular structures varying from linear to crosslinked ones depending on the structure, functionality and stoichiometry of the reactants. These thermosetting polymers cannot be reprocessed or reused if, according to the desired applications, chemical crosslinkers are used [16]. For de-crosslinking of polyurethane networks, dynamic covalent chemistry is used, especially by means of the DA and retro-DA (rDA) reactions [17]. Due to its reversibility the DA reaction also represents a choice to create self-healing properties for polymer networks [18]. Concerning polyurethane, the DA reaction was employed in thermally remendable linear polymers [19][20][21][22] and thermally reversible networks [23][24][25][26][27]. The latter were designed in three different ways: i) by polymerization reaction of monomers containing maleimide-furan cycloadduct [26,28], ii) by crosslinking of linear polyurethane containing furan or maleimide pendant groups [27,29,30] and iii) by cycloaddition DA reaction between polyurethane containing furan end groups and multimaleimide monomers [19,[23][24][25][31][32][33]. Abstract. Urethane bismaleimides (BMIs) were used in order to obtain crosslinked structures by their reaction with an aromatic trifuran compound. The Diels-Alder (DA) reaction between the maleimide and furan moieties was investigated using proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy for a model compound (CTF), due to the fact that the networks are insoluble in usual NMR solvents. The structure of the networks was confirmed by infrared spectroscopy. Thermal properties were investigated (by means of differential scanning calorimetry (DSC) and thermogravimetrical analyses (TGA)) and compared with the ones of similar compounds, previously obtained from the same BMIs and a different trifuran compound (which contains tertiary nitrogen in its structure). Mechanical and rheological properties were also investigated. The influence of the nature of the polyol from the BMIs structure and/or the influence of using a trifurylic compound with or without tertiary nitrogen on the properties of the crosslinked networks were also discussed.

Designing New Sustainable Polyurethane Adhesives: Influence of the Nature and Content of Diels–Alder Adducts on Their Thermoreversible Behavior

“…The 1 H NMR and 13 C NMR spectra of BMIF and DAF are displayed in Figures S1-S8. The signals observed in both spectra can be perfectly assigned to the chemical structure of DAF and are in good agreement with the data in the literature [15][16][17][18][19]. Moreover, the samples were free of unreacted BMI but bands corresponding to FA were clearly observed as expected due to the excess of FA in the feed.…”

Review of Progress in Shape Memory Epoxies and Their Composites

“…The oxazolidone chemistry is a useful way to tailor the hard segments in polyurethanes (PUs) [ 49 ]. Note that segmented PUs represent the most versatile and mostly researched family of SMPs [ 51 , 52 ]. Nowadays, the R & D works on shape memory polyurethanes are focused on potential medical applications.…”

One-Pot Synthesis and Characterization of Novel Shape-Memory Poly(ε-Caprolactone) Based Polyurethane-Epoxy Co-networks with Diels–Alder Couplings

“…There are numerous reports for the preparation EP-PU systems in which different interpenetrating network (IPN) were formed [ 7 , 8 , 9 , 10 , 11 , 12 ]. Furthermore, incorporations of Diels–Alder (DA) adducts into different polymeric systems have paved the way for the preparation of networks with thermally reversible couplings [ 13 , 14 , 15 , 16 ]. The related systems exhibit self-healing [ 17 , 18 , 19 ], shape memory (SM) behavior [ 20 , 21 ], and even a combination of self-healing and SM, denoted as Diels–Alder shape memory-assisted self-healing [ 22 ].…”