One-side non-covalent modification of CVD graphene sheet using pyrene-terminated PNIPAAm generated via RAFT polymerization for the fabrication of thermo-responsive actuators

Thermo-responsive graphene-polymer films have been obtained by the modification of large CVD graphene films with pyrene-terminated poly(N-isopropylacrylamide) (PNIPAAm) via non-covalent π-π stacking interactions. Pyrene-terminated PNIPAAm was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization using a pyrene-functionalized RAFT agent. Since PNIPAAm possesses a lower critical solution temperature (LCST) of 32 °C, the as-prepared graphene-PNIPAAm films could be reversibly deformed as a result of the morphology response of PNIPAAm to the environmental temperature variation. In addition, the thermo-triggered deformation of the graphene-PNIPAAm films was observed to be reversible and controllable by manipulation of the environmental temperature. Atomic force microscopy (AFM) and high-resolution SEM analysis evidenced the successful attachment of the PNIPAAm on the graphene surface. The thickness of the polymer was revealed by high-resolution scanning electron microscopy (SEM). The successful stepwise fabrication of the CVD graphene-polymer composite films was also characterized using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). These thermo-responsive composite films would be highly desirable for a wide range of applications, such as thermo-responsive actuators, a thermo-responsive intelligent switch was fabricated using these thermo-responsive graphene composite films.