A new monomer and its water-soluble polymer have been synthesized containing pendant methyl ether and carboxylic acid groups. This polymer was found to possess a lower critical solution temperature (LCST) in pure water that is dependent on added salt and almost independent of polymer concentration (above 3 x 10(-4) wt.%). Values of the LCST typically ranged from around 40-50 degrees C but decreased to 35 degrees C in 1% NaCl.