pH- and thermo-responsive dispersion of single-walled carbon nanotubes modified with poly(N-isopropylacrylamide-co-acrylic acid).

Single-walled carbon nanotubes (SWNTs) were homogeneously dispersed in the aqueous solution of poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAm-co-AA)) with the assistance of sonification as evidenced by UV-vis absorption spectroscopy, transmission electron microscopy, field emission scanning electron microscopy and atomic force microscopy, etc. In addition, the SWNTs were endowed with pH- and thermo-sensitivity at the same time. The SWNTs switched reversibly between the aggregated and the well-exfoliated states by using pH or temperature as a stimulus. Moreover, the factors including solvent composition while preparing P(NIPAm-co-AA), concentration and composition of P(NIPAm-co-AA) showed evident influence on the dispersing stability of SWNTs. The introduction of a tiny amount of acrylic acid to copolymerize with N-isopropylacrylamide could greatly enhance dispersing ability of SWNTs.