cloud points and phase separation of aqueous poly n vinylacetamide solutions in the presence of salts
Copyright policy )cloud points and phase separation of aqueous poly n vinylacetamide solutions in the presence of salts
Aqueous poly(N-vinylacetamide) (PNVA) solution was found to exhibit the cloud point in the presence of salt. This cloud point was shown to correspond to a liquid-liquid phase separation, as confirmed when the PNVA-salt solutions were maintained at a temperature above the cloud point. The upper layer had a higher polymer concentration and a lower salt concentration than those in the lower layer. Thus interaction between PNVA and salts are repulsive. The lower critical solution temperatures were estimated to be 18±1°C for 1.25 molal (NH4)2SO4 and 25±1°C for 0.76 molal Na2SO4. Divalent anions such as SO 2− 4 , SO 2− 3 , HPO 2− 4 and CO 2− 3 were effective in causing turbidity when examined at 25°C. Dependence of the effect on the cationic species was similar to but significantly different from that for acetyltetraglycine ethylester. The cloud points of PNVA decreased linearly with the increase of the polymer concentration at a fixed salt concentration or with the increase of the salt concentration at a fixed polymer concentration. A parameter analogous to the salting-out constant was empirically derived from the dependencies of the cloud points on the concentrations of polymer and salt.
- Kyushu University Japan
- Kagoshima University Japan
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