Effect of Urea on Phase Transition of Poly(N-isopropylacrylamide) Investigated by Differential Scanning Calorimetry

• DOI: 10.1021/jp503834c
• Publication Date: 2014-07-16T17:51:46Z
• Authors: Yating Gao; Jinxian Yang; Yanwei Ding; Xiaodong Ye
• Keywords: Endothermic process; Exothermic reaction; Poly(N-isopropylacrylamide); Endotherm

The effect of urea on the phase transition PNIPAM was studied using differential scanning calorimetry (DSC). For a certain concentration, enthalpy change poly(N-isopropylacrylamide) (PNIPAM) aqueous solution increases with number DSC cycles, presumably due to displacement water molecules bound amide groups by at temperature higher than lower critical (LCST) and causes decrease in absolute value exothermic heat related dehydration hydrophilic interactions residues around 0. Moreover, decreases concentration during heating process first cycle, indicating replacement apolar isopropyl LCST, endothermic caused decreases. Furthermore, which replace high can be replaced again but this needs several days complete.