Sol-Gel Transition Curve of Poly(vinylidene fluoride) in Organic Solvents
Risei WADA, Kiyotaka AIHARA, Hiroshi NOMOTO, Michiko TAZAKI and Masaru OKABE*
Department of Applied Chemistry, Faculty of Engineering, Kanagawa Institute of Technology; Shimo-ogino, Atsugi-shi 243-0292 Japan
It is well known that poly(1,1-difluoroethylene) (hereafter named poly(vinylidene fluoride) (PVdF)) dissolved in some ketones or lactones at high temperature forms a thermoreversible gel in the vicinity of room temperature. In this study, the interaction parameter (x12) between PVdF and solvent was estimated as a function of temperature by an inverse gas chromatography(IGC) method. The correlation between gelation of PVdF solution and the magnitude of x12 value was discussed. The solvents used were hexane, cyclohexanone, γ-butyrolactone, and N,N-dimethylformamide. Moreover, sol-gel transition curve was determined for four samples with different molecular weights.
The interaction parameter x12 obtained for each PVdF/solvent system increased slowly with decreasing temperature. The gelation of PVdF occurred with decreasing temperature for the following two systems: one was the system where the parameter x12 increased passing through 0.5 such as the system PVdF/cyclohexanone; the other was the system where x12 approached 0.5 such as the system PVdF/γ-butyrolactone. The sol-gel transition curve shifted to lower concentration with increasing molecular weight.
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