Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group?part 7. Copolymerization of tetrafluoroethylene with ?-hydroxy trifluorovinyl monomers

Abstract

The radical copolymerization of tetrafluoroethylene (TFE) and trifluorovinyl ω-hydroxy comonomers [F2CCF(CH2)mOH with m = 1 (FA1) and m = 3 (FA3)] for the synthesis of fluorinated polymers bearing hydroxy side groups is presented. FA1 was prepared by dehydrofluorination of 2,2,3,3-tetrafluoropropanol, whereas FA3 was obtained in a three-step scheme starting from the radical addition of 1,2-dichloroiodotrifluoroethane to allyl alcohol. The copolymerization conditions (in bulk or in solution in di n-butyl ether) and the polymer compositions considerably influenced the molecular weights, the molecular weight distributions, and the thermal properties of these copolymers. The kinetics of copolymerization of both couples enabled to determine the reaction order to the initiator (being 0.9) and the close values of apparent activation energies for [TFE/FA1 (Ea = 52.4 kJ · mol−1) and for TFE/FA3 (Ea = 46.8 kJ · mol−1)] couples. From the Tidwell and Mortimer method, the relative reactivity ratios were calculated by elemental analysis or by 19F-NMR spectroscopy, showing a higher reactivity of the TFE to incorporate the copolymer (rTFE = 2.47 and rFA1 = 0.41; rTFE = 1.57 and rFA3 = 0.45). The high values of the reaction order to the initiator and low molecular weights of copolymers were associated to the allylic chain transfer of the hydroxy comonomers and a mechanism of copolymerization was proposed. The comonomer diad and triad distribution was determined by the statistic theory and allowed one to calculate the average length of the comonomer sequences. Finally, the thermal decomposition of these cooligomers showed that those containing FA3 units are more thermostable than those synthesized from FA1, and that the higher the fluorinated alcohol content, the faster the thermal decomposition. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 189–202, 1999