Surface modification of polyurethane nanocomposite films via nonsolvent‐induced phase separation accelerated by graphene nanoplatelets

Abstract Polyurethane (PU) nanocomposite films were prepared through a solution casting technique slightly modified by individual and simultaneous additions of a proper nonsolvent (ethanol) and graphene nanoplatelets. To this end, different nonsolvent contents and graphene functionalizations (hydrophobic and hydrophilic) were used to modify the surface properties of PU to make it more biocompatible. X‐ray diffraction patterns revealed that both types of graphene had a hampering effect on crystallization of PU from solution, while nonsolvent enhanced the PU crystallinity. According to morphological results, hydrophobic graphene showed a low dispersion quality. In contrast, the hydrophilic graphene was better dispersed and mainly localized at the bulk of the film due to its association with polar urethane groups in the hard segments. Wettability analysis, performed by water and diiodomethane, was employed to demonstrate a higher surface localization of hard segments for the samples loaded with hydrophilic graphene. Cytotoxicity analysis also showed a greater extent of cell viability for the samples loaded with hydrophilic graphene, demonstrating a direct correlation between biocompatibility and polar hydrophilic groups enriching the surface. This study shows the great potential of graphene in improving the nonsolvent‐induced phase separation to achieve a more biocompatible material.