Anionic polymerization of fluorine-substituted phenyl methacrylates

Synthesis and anionic polymerization of the fluorine-substituted phenyl methacrylates are herein reported. A series of mono-, di-, and multi-substituted fluorophenyl methacrylates H2C=C(CH3)C(O)OC6H4F-4 (M1a), H2C=C(CH3)C(O)OC6H4F-3 (M1b), H2C=C(CH3)C(O)OC6H3F2-2,4 (M2), H2C=C(CH3)C(O)OC6H2F3-2,3,4 (M3), H2C=C(CH3)C(O)OC6HF4-2,3,5,6 (M4), and H2C=C(CH3)C(O)OC6F5 (M5) were synthesized and characterized. Initially, the polymerization was carried out on the monomer M1a by using nBuLi, tBuLi, and KH as the respective catalysts; this approach produced the polymers in yields of 12%–50%, but with lower molecular weights. Similar results were obtained by using tBuLi for catalytically polymerizing the other five monomers. By introducing a co-catalyst MeAl(BHT)2, the catalysts NaH, LiH, and tBuOLi each were tested to polymerize M1a, which gave the polymers in very low yields (3%–7%). Polymer yields of 13%–27% were obtained by each of the catalysts LiAlH4, nBuLi, PhLi, and tBuLi in connection with MeAl(BHT)2, but a better yield (61%) was achieved with KH/MeAl(BHT)2. The KH/MeAl(BHT)2 catalyst system was further employed to polymerize M1b and M2, which afforded respective polymer yields of 12%–63% and 10%–53%, depending on the molar ratios of KH:MeAl(BHT)2 as well as on the monomer concentrations. All of the polymers produced were syndiotactically rich in structure, as indicated by either 1H or 19F NMR data. The polymerization mechanism by the combined catalyst system is proposed.