Synthesis and surface modification of sunflower oil‐based non‐isocyanate polyurethane: Physicochemical and antibacterial properties

Abstract In this work, non‐isocyanate polyurethane (NIPU) films are synthesized from sunflower oil (SFO) with the object of using a renewable resource and establishing a nonpolluting process. SFO also has the advantage of having a higher level of unsaturation than other commercial oils, which provides more reactive sites to be chemically modified. This feature enables a higher degree of conversion to the two monomers, cyclocarbonate, and polyamine‐polyol. NIPU is obtained from their mixture and further crosslinking at 90°C allows the films with suitable mechanical properties to be used in biomedical applications. However, NIPU does not show antibacterial activity, so the surface must be modified. Two methods are used: layer‐by‐layer coating of alginate‐chitosan, and immersion in tea tree oil (TTO), previously activating the surface with acrylic acid (AANIPU). Surface modifications are confirmed by increased hydrophilicity, thermochemical changes, and a drop in mechanical performance. TTO on NIPU films inhibits bacterial growth against S. aureus and E. Coli . NIPU and AANIPU can be accepted as noncytotoxic, while incorporation of the two agents can produce cytotoxicity. No previous reports of such modifications have been found on NIPU films, which appear as promising alternatives for biomedical applications.