Carboxymethylcellulose Grafted to Amino-Terminated Poly(-isopropylacrylamide): Preparation, Characterization and Evaluation of the Thermoassociative Behaviour at Low Concentrations

摘要

Amino-terminated poly(N-isopropylacrylamide) (PNIPAM-NH2) was syn- thesized by free-radical polymerization in water by using the redox pair potassium persulfate/2-aminoethanethiol hydrochloride (KPS/AET.HCl) in a glove box under N_(2(g)) atmosphere. PNIPAM-NH2 was then used to produce graft copolymers with carboxymethylcellulose (CMC) in water by applying a water-soluble carbodiimide and N-hydroxysuccinimide as activators. The samples were characterized by infrared spectroscopy and the thermal behaviour on solid state was investigated by thermogravimetry. Also, the rheological behaviour of the copolymers at 25 and 60 ° C was evaluated in water at 3 and 7 g/L. Contrary to CMC and PNIPAM-NH2, which had only one DTG peak, the thermal decomposition of the graft copolymers occurred at two steps, being the first DTG peak higher and second one lower than the corresponding precursors. Thermoassociative behaviour in water for CMC-g-PNIPAM graft copolymers depend on the amount of chain transfer agent used for the PNIPAM-NH2 synthesis. Thermothickening effect occurred for the copolymer that had PNIPAM-NH2 prepared with lower AET.HCl content, at a polymer concentration of 7 g/L, which is much lower than the concentrations previously reported in literature for graft copolymers with poly(N-isopropylacrylamide).