Reduction Performance and Mechanism of Liquid Terminated-Carboxyl Fluoroelastomers Using Unitary or Binary Metal Hydride Reduction Systems

Unitary metal hydride reduction systems (diisobutyl aluminum hydride and lithium aluminum hydride) and binary metal hydride reduction systems (sodium borohydride/diisobutyl aluminum hydride and lithium aluminum hydride/diisobutyl aluminum hydride) were used to reduce liquid terminated-carboxyl fluoroelastomers (LTCFs). LTCFs were efficiently converted to the corresponding liquid terminated-hydroxyl fluoroelastomers (LTHFs) via a simple one-pot method. The reductive rate of LTHFs was analyzed by chemical titration. The structure of LTCFs and LTHFs was analyzed by Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance (¹H NMR) spectroscopy and ¹⁹F nuclear magnetic resonance (¹⁹F NMR) spectrocopy. The results show that –C=C– and carboxyl groups of LTCFs are reduced efficiently. The effect of unitary metal hydride reduction systems and binary metal hydride reduction systems on the performances of the LTCFs reduction was compared. The results show binary metal hydride reduction systems are more efficient for reduction of LTCFs at ambient temperature. In addition, sodium borohydride/diisobutyl aluminum hydride binary metal hydride reduction system achieves the highest reductive rate (93%) and its reductive mechanism was investigated.