Fluoroalkyl Pentacarbonylmanganese(I) Complexes as Initiators for the Radical (co)Polymerization of Fluoromonomers

The use of [Mn(R-F)(CO)(5)] (R-F = CF3, CHF2, CH2CF3, COCF2CH3) to initiate the radical polymerization of vinylidene fluoride (F2C=CH2, VDF) and the radical alternating copolymerization of vinyl acetate (CH2=CHOOCCH3, VAc) with tert-butyl 2-(trifluoromethyl)acrylate (MAF-TBE) by generating primary R-F(center dot) radicals is presented. Three different initiating methods with [Mn(CF3)(CO)(5)] (thermal at ca. 100 degrees C, visible light and UV irradiations) are described and compared. Fair (60%) to satisfactory (74%) polyvinylidene fluoride (PVDF) yields were obtained from the visible light and UV activations, respectively. Molar masses of PVDF reaching 53,000 gmol(-1) were produced from the visible light initiation after 4 h. However, the use of [Mn(CHF2)(CO)(5)] and [Mn(CH2CF3)(CO)(5)] as radical initiators produced PVDF in a very low yield (0 to 7%) by both thermal and photochemical initiations, while [Mn(COCF2CH3)(CO)(5)] led to the formation of PVDF in a moderate yield (7% to 23%). Nevertheless, complexes [Mn(CH2CF3)(CO)(5)] and [Mn(COCHF2)(CO)(5)] efficiently initiated the alternating VAc/MAF-TBE copolymerization. All synthesized polymers were characterized by H-1 and F-19 NMR spectroscopy, which proves the formation of the expected PVDF or poly(VAc-alt-MAF-TBE) and showing the chaining defects and the end-groups in the case of PVDF. The kinetics of VDF homopolymerization showed a linear ln[M](0)/[M] versus time relationship, but a decrease of molar masses vs. VDF conversion was noted in all cases, which shows the absence of control. These PVDFs were rather thermally stable in air (up to 410 degrees C), especially for those having the highest molar masses. The melting points ranged from 164 to 175 degrees C while the degree of crystallinity varied from 44% to 53%.