Non-isocyanate polyurethane hydrogels: investigation of mechanical properties
Antoine Delvaux, Raphaël Riva, Bruno Grignard, Christophe Detrembleur, Christine Jérôme
Nowadays, polyurethanes (PU) are listed among the most versatile families of polymers. They are used in a wide range of applications, from foams to hydrogels[1]. Within the hydrogel sector, PU are found in various formulations designed for different uses, such as water depollution, wound dressing, and drug delivery[2]. This wide application range is due to the large diversity of commercially available PU building blocks, allowing to achieve various physico-mechanical properties. However, PU are increasingly becoming the target of regulations due to their traditional synthesis method, which involves the use of di-isocyanates. These chemicals have been proven to be strong irritants and are also flammable and explosive. Furthermore, their synthesis requires hazardous chemicals, as di-isocyanates are produced through the phosgenation of amines[3].
To address the need for safer PU formulations, non-isocyanate polyurethanes (NIPU) have been investigated[4]. A promising strategy lies in the reaction between polyamines and α-alkylidene bis-cyclic carbonates, which forms a polyoxazolidone-based material[5]. Indeed, many polyamines are readily available and the structure of the spacer of the bis-cyclic carbonate can be modified to fine-tune the mechanical properties of the resulting material. Here, based on this strategy, we synthesized a variety of NIPU hydrogels by exploring the reaction of Jeffamine with bis-cyclocarbonates exhibiting different spacers in the presence of a crosslinker. We investigated the impact of the NIPU formulation composition on the mechanical properties of the resulting networks in the dry state so as of the hydrogels obtained by swelling in aqueous media.