Effect of additives on the cloud points of aqueous solutions of ethylene oxide-propylene oxide-ethylene oxide block copolymers

The cloud points of aqueous solutions of eight ethylene oxide (EO)/propylene oxide (PO) triblock copolymers were measured in the presence of eight additives. The additives increased these temperatures in the following sequence: urea, dimethylurea, tetrapropylammonium bromide < nicotinamide < sodium thiocyanate < sodium p-toluenesulfonate < sodium xylenesulfonate < tetrabutylammonium bromide. No similar trend could be derived in relation to the polymers structure or composition. The same additives were tested with two ethoxylated nonylphenols and with three PPO and were only effective to increase the cloud points of compounds containing EO chains. This observation suggests that these additives affect the solvation capacity of water in relation to the EO units, especially at higher temperatures. (C) 1998 Academic Press.