Thermoresponsive phase transition behaviors of poly(

N

-vinylcaprolactam) (PNVCL) in water-solvent mixtures were investigated. Several aprotic solvents including dimethyl sulfoxide (DMSO)

N

N

-dimethylformamide (DMF)

tetrahydrofuran (THF)

1

4-dioxane and protic solvents (low molecular weight alcohols) were selected and phase separation temperatures were determined by turbidity measurements using UV-Vis spectroscopy. The results showed that the low critical solution temperatures (LCSTs) of PNVCL increased monotonically with increasing concentration of added DMF

THF

1

4-dioxane and CH

3

OH to the aqueous solution of PNVCL. The addition of DMF and 1

4-dioxane had the greatest effect on the LCSTs of PNVCL

followed by THF

while methanol has the least effect on its LCST. The addition of small amounts of ethanol

1-propanol

and 2-propanol to an aqueous PNVCL solution initially decreases the transition temperature

and a further addition increases it. Unlike these alcohols

the LCST of PNVCL gradually increases up to

x

DMSO

=0.1 and then decreases with increasing concentration of added DMSO.