Síntese, caracterização e estudo da associação em meio aquoso de copolímeros responsivos de carboximetilcelulose-g-Jeffamine®

This thesis presents the synthesis, characterization and study of the associative behaviour in aqueous media of new responsive graft copolymers, based on carboxymethylcellulose as the water-soluble backbone and Jeffamine® M-2070 e Jeffamine® M-600 (commercial polyetheramines) as the thermoresponsive grafts with high cloud point temperatures in water. The synthesis was performed on aqueous medium, by using 1-ethyl-3- (3-(dimethylamino)-propyl)carbodiimide hydrochloride and N-hydroxysuccinimide as activators of the reaction between carboxylategroupsfrom carboxymethylcellulose and amino groups from polyetheramines. The grafting reaction was confirmed by infrared spectroscopy and the grafting percentage by 1H NMR. The molar mass of the polyetheramines was determined by 1H NMR, whereas the molar mass of CMC and graft copolymers was determined by static light scattering. The salt effect on the association behaviour of the copolymers was evaluated in different aqueous media (Milli-Q water, 0.5M NaCl, 0.5M K2CO3 and synthetic sea water), at different temperatures, through UV-vis, rheology and dynamic light scattering. None of the copolymers solutions, at 5 g/L, turned turbid in Milli-Q water when heated from 25 to 95 °C, probably because of the increase in hydrophibicity promoted by CMC backbone. However, they became turbid in the presence of salts, due to the salting out effect, where the lowest cloud point was observed in 0.5M K2CO3, which was attributed to the highest ionic strength in water, combined to the ability of CO3 2- to decrease polymer-solvents interactions. The hydrodynamic radius and apparent viscosity of the copolymers in aqueous medium changed as a function of salts dissolved in the medium, temperature and copolymer composition. Thermothickening behaviour was observed in 0.5M K2CO3 when the temperature was raised from 25 to 60°C. This performance can be attributed to intermolecular associations as a physical network, since the temperature is above the cloud point of the copolymers in this solvent.