ATRP graft copolymerization of poly(N-isopropylacrylamide-co-acrylic acid) on multiwalled carbon nanotubes

The polymer functionalized multiwalled carbon nanotubes (MWCNT) have been prepared by atom transfer radical graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) monomers from their binary mixture at fixed feed molarity and composition (f (NIPAAm) ). The donor-acceptor interactions between acrylic acid and N-isopropylacrylamide have enhanced the activity of N-isopropylacrylamide for grafting onto MWCNT (52%) in comparison to individual grafting of N-isopropylacrylamide onto MWCNT (38%). The CuBr and N'N'N'N'N'-pentamethyldiethylenetriamine (PMDETA) were used as ATRP catalysts for graft copolymerization of N-isopropylacrylamide and acrylic acid onto multiwalled carbon nanotubes. The copolymers grafted onto MWCNT were of high molecular weight (42x10(3) g mol(-1)) with low molecular weight dispersity (1.13) at 0.1 M a feed molarity and feed composition (f (NIPAAm) ) of 0.6. The graft yield (%G), molecular weight (MW), and sequence length of N-isopropylacrylamide and acrylic acid monomers (mM(1) an mM(2)) in the grafted chains varied significantly with varying feed composition (f (NIPAAm) ). The grafting produced highly water soluble multiwalled carbon nanotubes in comparison to pristine MWCNT. The grafted copolymer chain dispersity varied with solution temperature and pH due to the temperature and pH sensitivity of the monomers. The poly(N-isopropylacrylamide-co-acrylic acid) grafted chains were characterized by FT-IR and NMR techniques for their structures and thermal stability as determined by TGA.