Thermal Analysis of the Volume Phase Transition with N-Isopropylacrylamide Gels

Katsuto Otake, Hiroshi Inomata, Mikio Konno, Shozaburo Saito

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729 Citations (Scopus)


Experimental work was done to study the thermoshrinking-type volume phase transition of N-isopropylacrylamide (NIP A) gel in aqueous solutions. The experiments principally consisted of the application of thermal analysis with a differential scanning calorimeter (DSC) to NIPA gels and to aqueous solutions of linear NIPA polymer (PNIPA) and poly(vinyl methyl ether) (PVME), whose gel is characteristic of the thermoshrinking type. The transition temperatures of NIPA gel obtained from DSC analysis were compared with those usually obtained from standard swelling experiments. This comparison clarified the efficiency of DSC for the determination of the transition temperature. For the linear polymer solutions, the transition temperatures obtained from DSC were satisfactorily consistent with their cloud points. Both the transition temperature and heat of the collapse of the NIPA gel showed similar values to those of the PNIPA solutions, which permitted the inference that the volume phase transition is controlled primarily by the same factors as the coil-globule transition of the linear polymer. The transition heat of collapse of the gel was endothermic and its absolute value was larger than those reported for nonpolar organic solution systems. Similar results were obtained with the linear polymer solutions. The experimental results were interpreted by using the concept of hydrophobic interaction. The addition of low molecular weight substances changed the transition temperature. This can be explained through the viscosity B coefficient.

Original languageEnglish
Pages (from-to)283-289
Number of pages7
Issue number1
Publication statusPublished - 1990 Jan 1

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry


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