On the upper critical solution temperature of PNIPAAM in an ionic liquid: Effect of molecular weight, tacticity and water
The upper critical solution temperature (UCST) of 1.0 wt% Poly(N-isopropylacrylamide) (PNIPAAM) in the ionic liquid (IL) 1-ethyl-3-methylimidazolium-bis(trifluoromethanesulfonyl)amide ([EMIM][TFSI]) is strongly affected by the molecular weight and tacticity of the polymer and water content of the IL. UCSTs in IL/water mixtures are tuned in a wide range by modulating the abovementioned parameters: notably UCST spans from about -12 °C for atactic and low MW PNIPAAM in anhydrous IL up to 79 °C for the stereo-regular high MW one in presence of water.