Temperature-sensitive and highly water-soluble titanate nanotubes

Water-soluble titanate nanotubes (TNTs) with temperature-responsive shells were synthesized by grafting poly(N-isopropylacrylamide) (PNIPAAm) from TNTs via surface atom transfer radical polymerization (ATRP) using ATRP agent functionalized TNTs as macroinitiator. Proton Nuclear magnetic resonance spectroscopy (1H NMR), Fourier-transform infrared (FT-IR) and thermogravimetric analyses (TGA) results prove the successful graft of PNIPAAm chains from TNTs. TGA shows that the amount of PNIPAAm grown from the TNTs increased with the increase of monomer/initiator ratio. Transmission electron microscope (TEM) measurements displays the obtained TNTs-g-PNIPAAm nanohybrids have a core-shell structure of TNT cores and PNIPAAm shells. In addition, the functional nanotubes demonstrate a reversible low critical solution temperature (LCST) transition with the increase of solution temperature. The synthetic method presented here can also be extended to graft other stimuli responsive polymers from TNTs.