Ring-opening polymerization of 1-phenyl-20vinylcyclopropane derivatives by ziegler-natta catalysts

Abstract

p-Substtituted phenylvinylcyclopropanes, 1-phenyl-2-vinyl-cyclopropane, 1-(p-anisyl)-2-vinylcyclopropane, 1-(p-tolyl)-2-vinylcyclopropane, 1-(p-chlorophenyl)-2-vinyl-cyclopropane and 1-(p-cyanophenyl)-2-vinylcyclopropane, were synthesized and polymerized with various initiators such as Ziegler-Natta catalysts. Their polymerization behavior, characterization and the properties of the resulting polymers were also investigated. Those five p-substituted phenylvinylcyclopropanes exhibited quite different polymerization behavior depending on the properties of their substituents. Polymerization results showed that the monomers with electron-donating substituents were readily polymerizable with Ziegler-Natta catalysts and cationic initiators, whereas the monomers with electron-withdrawing groups were not. And the opposite trend was observed in the polymerization with radical initiators. In the polymerization of methoxy- and methyl-substituted monomers, acidic organoaluminum compounds such as $AlEtCl_2$ based on metal halides were very effective cocatalysts. Ziegler-Natta polymerization is considered to proceed through the proposed coordination mechanism in which a monomer molecule is first coordinated at the catalyst site before propagation and the propagating species then attacks the activated benzylic carbon position of the coordinated monomer to yield 1,5-addition polymers. In radical polymerization of chloro- and cyano-substituted monomers, the reaction is considered to proceed through a mechanism in that a radical attacks at first on the vinyl group to form a cyclopropylcarbinyl radical and then this radical isomerizes to an allylcarbinyl radical with ring-opening. Allylcarbinyl radical will then react with another monomer to propagate. The polymers produced were confirmed to have the structures of five carbon-repeating unit and the double bonds in the polymer chain were in trans form. All the polymers were soluble in common solvents and flexible film-forming mate...