Sol-gel transition of poly(1,1-difluoroethylene) in gamma-butyrolactone/cyclohexanone mixed solvent

Poly(1, 1-difluoroethylene) (hereafter named poly(vinylidene fluoride) (PVd F)) in the mixed solvent of gamma-butyrolactone/cyclohexanone converts to t hermally reversible gel. Gelation process of PVdF in the mixed solvent was investigated by Fourier transform infrared(FT-IR) measurement and gelation time (t(gel)) was measured as a function of composition of cyclohexanone (X -cyclo) in the mixed solvent. FT-IR spectra suggested that gelation of PVdF in gamma-butyrolactone/cycloh exanone mixed solvent occurred through crystallization of polymers taking t wo Binds of conformations, T(3)GT(3)(G) over bar and TGT (G) over bar. t(ge l) increased slowly with increasing X-cyclo, and showed maximum value at X- cyclo = 30 vol%, then decreased with increasing X-cyclo According to measur ement of cloud temperature of PVdF solution, the mixed solvent showed the m aximum solvent power at X-cyclo = 30 vol%. That is, cosolvency appeared at this composition. It is considered, therefore, that crystallization and gel ation of PVdF in the mixed solvent proceed very slowly at X-cyclo =30 vol%.