화학공학소재연구정보센터
Macromolecules, Vol.42, No.3, 612-619, 2009
Anionic Ring-Opening Polymerization of Hexafluoropropylene Oxide Using Alkali Metal Fluorides as Catalysts: A Mechanistic Study
The anionic ring-opening polymerization of hexafluoropropylene oxide using the conventional alkali metal fluorides/tetraglyme catalytic system in the presence of different fluorinated solvents at various temperatures and under batch conditions is reported. Basically, the sodium fluoride (NaF)/tetraglyme system gave only monoadduct CF3CF2CO2CH3, while cesium fluoride (CsF)/tetraglyme produced oligomeric product with number-average degree of polymerization (DPn) less than 5. The higher molar mass polymers were synthesized using the potassium fluoride (KF)/tetraglyme catalytic system and 1,1,1,3,3-pentafluorobutane (C4F5H5) or 1,3-bis(trifluoromethyl)benzene as solvent at 0 degrees C. Under these conditions, polymers with number-average molar masses ranging between 2500 and 3500 g mol(-1) were obtained in high contents (>90%) and almost without any low molar mass (DPn <= 5) contaminants (4-7%). Polymers which chain ends were derived into methyl esters were fully characterized by gas chromatography, F-19 and H-1 NMR, and MALDI-TOF-MS spectroscopy. A kinetic study allowed us to propose a tentative mechanism entailing (i) the livingness of the polymerization of the hexafluoropropylene oxide with KF/tetraglyme catalytic system and (ii) the importance on the control of molar masses of the biphasic gas/liquid environment in the batch autoclave.