Renewable adhesives based on oleo-chemistry: From green synthesis to biomedical applications

Polyurethanes (PUs) are known as performing biomedical tissue adhesive materials. Adhesive applications can be based on synthesized PU-based prepolymers with highly reactive isocyanate (NCO) end-chains, which covalently react with surrounding living tissues. In this study, original sustainable macromolecular architectures were designed and tested. Different fully biobased polyfunctional NCO terminated prepolymers were synthesized from cotton oil (CO)-based polyols and different sustainable diisocyanates (l-Lysine ethyl ester diisocyanate (LDI), pentane diisocyanate (PDI) and dimeryl diisocyanate (DDI)). Then, two-component adhesive systems were prepared using the prepolymers and two chain extenders: 1,4-butanediol and 2-hydroxyethyl disulfide, to obtain in this latter case potential stimuli-responsive materials based on the disulfide bonds. Prepolymers' properties such as in-vitro biocompatibility, as well as two-components systems' adhesive behavior on muscle tissue were assessed. From these two-component systems, fully biobased PUs were obtained. The influence of the selected CO-based polyol, the diisocyanate and the chain extender on the physicochemical, thermal and mechanical properties of the corresponding PUs were studied. Moreover, their influence on biocompatibility and properties related to biomedical applications were discussed. The series of PUs exhibited a large range of properties such as Young's moduli at 25 and 37 °C, ranging from 0.4 to 22 MPa, and adequate hydrolytic and enzymatic degradations after nine weeks of incubation. LDI and PDI-based samples showed great interest in the preparation of such biomedical adhesives due to their good biocompatibilities.