Sol-Gel Transition and Interaction between Fluorine-Contained Polymer/Organic Solvents

点击翻译按钮获取中文摘要

The Flory-Huggins interaction parameter (χ_12) of poly(vinylidene fluoride)(PVdF)/organic solvent system was measured over wide range of temperature by an inverse gas chromatography (IGC) using many kinds of solvents such as alkane, alkene, ketone, lactone, and nitrogen-containing solvent. The thermoreversible gelation of PVdF solution was discussed from the magnitude of interaction parameter χ_12 between PVdF and solvent. The parameter χ_12 was measured for a concentrated PVdF solution by the usual IGC technique.The parameter χ_12 obtained for each PVdF/solvent system increased slowly with decreasing temperature. The present systems were divided into three groups according to the magnitude of χ_12 in the vicinity of room temperature, i.e., group (a) with χ_12>> 0.5, group (b) with χ_12 ≒ 0.5, and group (c) with χ_12 << 0.5. The group (b), to which ketone and lactone belong, converted to thermoreversible gels accompanying with crystallization of polymer.The gelation process of PVdF/organic solvent system was investigated through measurement of in situ Fourier transform infrared (FT-IR) spectroscopy. The time-resolved FT-IR spectra suggested that the sol-gel transition took place taking the conformation T_3GT_3G' for the system where the parameter χ_12 was nearly equal to 0.5 such as PVdF in γ-butyrolactone. For the system where the parameter χ_12 became larger than 0.5 such as PVdF in cyclohexanone, 3-pentanone, 3-hexanone, 3-heptanone, or 3-octanone, the sol-gel transition occurred taking the conformation TGTG'.