Efficient Grafting of Hyperbranched Polyglycerol from Hydroxyl-Functionalized Multiwalled Carbon Nanotubes by Surface-Initiated Anionic Ring-Opening Polymerization

Biocompatible hyperbranched polyglycerol (HPG) has been covalently grafted from the surfaces of multiwalled carbon nanotubes (MWNTs) by the grafting from method based on in situ anionic ring-opening polymerization. The macroinitiator of hydroxyl-functionalized MWNTs (MWNT-OH) with hydroxyl density of 1.39 mmol per gram of nanotubes was prepared by one-pot nitrene chemistry in N-methyl-2-pyrrolidone (NMP) at 160 degrees C for 12 h. The amount of HPG grafted from MWNTs can be readily adjusted in a wide range up to 90.8wt.-% by tuning the feed ratio of glycidol to MWNT-OH. The resulting HPG-grafted MWNTs (MWNT-g-HPG) nanohybrids were characterized by TGA, FT-IR, and NMR spectroscopy, HRTEM, and SEM. The as-prepared nanohybrids show good dispersibility in polar solvents such as water, DMF, DMSO, and methanol. On the basis of numerous functional hydroxyl groups of the HPG grown on MWNTs, fluorescent molecules of rhodamine 6B were conjugated to the surface of MWNT-g-HPG by N, N'-dicyclohexylcarbodiimide (DCC) coupling, affording fluorescent MWNTs. The multifunctional MWNT-g-HPG nanohybrids promise potential applications in drug delivery, cell imaging and bioprobing.