Thermosensitive Graphene Nanocomposites Formed Using Pyrene-Terminal Polymers Made by RAFT Polymerization

Thermosensitive graphene-polymer composites have been prepared by attaching poly(N-isopropylacrylamide) (PNIPAAm) onto the basal plane of graphene sheets via pi-pi stacking. Pyrene-terminated PNIPAAm was synthesized using reversible addition fragmentation chain transfer (RAFT) polymerization via a pyrene-functional RAFT agent. Aqueous solutions of the graphene-polymer composites were stable and thermosensitive. The lower critical solution temperature (LCST) of pyrene-terminated PNIPAAm was measured to be 33 degrees C. When the pyrene-functional polymer was attached to graphene the resultant composites were also thermosensitive in aqueous solutions exhibiting a reversible suspension behavior at 24 degrees C. Atomic force microscopy (AFM) analysis revealed that the thickness Of a graphene-PNIPAAm (M-n: 10,000 and PDI: 1.1) sheet was similar to 5.0 nm. The surface coverage of polymer chains on the graphene basal plane was calculated to be 7.2 x 10 (11) mol cm(-2). The graphene-PNIPAAm composite material was successfully characterized using X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR-IR) spectroscopy, and thermogravimetric analysis (TGA). (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 425-433, 2010