MWNTs were modified by amphiphilic polymer poly(vinyl pyrrolidone) (PVP) with ultrasonic assistance methods.The modified MWNTs were characterized by Fourier transform infrared spectroscopy (FTIR)

thermogravimetry (TG)

high-resolution transmission electron microscopy (TEM) and Raman spectrum.The results show that the surface of modified MWNTs was covered by PVP at special conditions.Modified MWNTs exhibit remarkable dispersion in water

glycol and dimethyl formamide (DMF).FTIR spectrum analysis show that amphiphilic polymer existsd on the surface of MWNT.Raman spectrum analysis show that the G band of modified MWNTs shifts to high wavenumber and is divided into two bands

which indicates that the chemical graft reaction has occurred between MWNTs and the amphiphilic polymer.TEM shows that the amphiphilic polymer unevenly covered on the surface and ends of modified MWNTs.The content of the amphiphilic polymer had little effect on graft mass

but the ultrasonic time affected the graft mass greatly

and the graft mass of PVP reached a maximum

when the ultrasonic time was 4 h.The modifying effect of the amphiphilic polymer was different from that of surfactant.MWNTs modified with surfactant SDBS can't dissolve in water again after washing and filtration

but MWNTs modified with amphiphilic polymer can dissolve in water again.