Aqueous solution behavior of new thermoassociative polymers

A new kind of water-soluble polymer was obtained by grafting side chains, characterized by a phase separation on heating (Lower Critical Solution Temperature LCST), on a hydrosoluble backbone. For semidilute solutions, the side chains associate as the temperature exceeds a critical temperature (T_ass), which is close to their LCST. Microdomains are formed which act like physical crosslinking units between the main chains, and an increase in the aqueous solution viscosity is observed. Systems based on 2-Acrylamido-2-methyl propane sulfonic acid (AMPS) backbone and polyethylene oxide (PEO) side chains were developed. Their rheological behavior in both dilute and semi-dilute states was studied by varying differents parameters such as polymer and salt concentrations, grafting ratio, etc. Fluorescence measurements indicate the formation of hydrophobic microdomains on heating, in agreement with the thickening properties of the solutions.