Preparation, structure and properties of metal-copolymer complexes of poly-4-vinylpyridine radiation-grafted onto polymer films

Copolymer products were prepared by radiation grafting of 4-vinylpyridine onto films of low-density poly(ethylene) and poly(tetrafluoroethylene) (PE-graft-P4VP and PTFE-graft-P4VP, respectively). The corresponding metal complexes were in turn obtained by interaction of the radiation-grafted copolymers with aqueous solutions of various salts such as FeCl3 · 6H2O, CoCl2 · 6H2O, VOSO4 · 5H2O, Na2MoO4 · 2H2O and Na2WO4 · 2H2О at room temperature. The content of metal ions was found to be within 0.53-10.93 mg metal/g polymer carrier. The polymer-supported metal complexes were identified by infrared spectroscopy and electron paramagnetic resonance analyses. The structure of the iron-containing polymeric materials was evaluated by Mossbauer spectroscopy. Some of the modified copolymers were also studied as polymer-supported catalysts of model reactions such as oxidation of cyclohexene with organic hydroperoxides. The catalytic activity of the molybdenum-containing polymer complex catalyst (P4VP-MoO22+) in the principal epoxidation reaction was higher than that of the vanadium-containing (P4VP-VO2+) one, whereas, the opposite order of activities was found for the side reaction of allylic hydroxylation of cyclohexene. Under selected reaction conditions, the yields of the principal reaction products cyclohexene oxide (1,2-epoxycyclohexane) and 2-cyclohexene-1-ol were 76.2% and 18.0%, respectively.