Functionalized carbon nanotubes modulate the phase transition behavior of thermoresponsive polymer via hydrophilic-hydrophobic balance

Abstract The world of nano-science is getting popularity due to their vast applications in the field of material science, biotechnology and biomedical research. In this context, carbon-nanotubes (CNTs) have provided new horizons because of their use as molecular transporters. Nonetheless, the low solubility in molecular solvents and cytotoxity of CNTs prevent their utility in biological process. Here, we established increasing solubility and dispersion of CNTs by functionalization with –COOH group that overcome these fundamental limitations. In spite of a broad range of applications of CNTs, it is highly desirable to examine the effect of functionalized CNTs (fCNTs) on the thermoresponsive polymers. In this respect, we have examined the effect of fCNTs on the thermoresponsive behavior of aqueous poly( N -isopropylacrylamide) (PNIPAM) solution by using several techniques such as dynamic light scattering (DLS), differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy and Field emission scanning electron microscope (FESEM). The present results indicate that the presence of fCNTs causes a small increase in the lower critical solution temperature (LCST) of PNIPAM which becomes more pronounced at lower concentration of fCNTs. It reveals that fCNTs indirectly favors the hydrophilic interactions of surrounded water molecules with PNIPAM that eventually stabilizes the coil state of PNIPAM.