Sol-Gel Transition of Poly (1,1-difluoroethylene) in γ-Butyrolactone/
Cyclohexanone Mixed Solvent

Risei WADA, Yuichi SATO, Michiko TAZAKI and Masaru OKABE*

Department of Applied Chemistry, Faculty of Engineering, Kanagawa Institute of Technology;
Shimo-ogino 1030, Atsugi-shi 243-0292 Japan

Poly (1,1-difluoroethylene) (hereafter named poly (vinylidene fluoride) (PVdF)) in the mixed solvent of γ-butyrolactone/cyclohexanone converts to thermally reversible gel. Gelation process of PVdF in the mixed solvent was investigated by Fourier transform infrared (FT-IR) measurement and gelation time (tgel) was measured as a function of composition of cyclohexanone (Xcyclo) in the mixed solvent.
FT-IR spectra suggested that gelation of PVdF in γ-butyrolactone/cyclohexanone mixed solvent occurred through crystallization of polymers taking two kinds of conformations, T3GT3 and TGT. tgel increased slowly with increasing Xcyclo, and showed maximum value at Xcyclo30 vol%, then decreased with increasing Xcyclo. According to measurement of cloud temperature of PVdF solution, the mixed solvent showed the maximum solvent power at Xcyclo30 vol%. That is, cosolvency appeared at this composition. It is considered, therefore, that crystallization and gelation of PVdF in the mixed solvent proceed very slowly at Xcyclo30 vol%.

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