Ziegler-Natta substituted styrenes

The mechanism of the isospecific polymerisation of styrene and its ring-substituted analogues in the presence of heterogeneous Ziegler-Natta catalysts is the same as for x-olefins. As regards the mode of monomer insertion, it has been reported as primary (1,2) insertion [37,38]. 

Beside the homopolymerization of BD Nd-based Ziegler/Natta catalyst systems are also applied for the homopolymerization of IP, the copolymerization of the dienes BD and IP, the homopolymerization and copolymerization of substituted dienes as well as for the copolymerization of BD with alkenes such as styrene, ethylene and other ethylene derivatives. 

Polyfluorostyrenes are described in many publications. A (3-fluorostyrene can be formed by cationic mechanism [289]. The material softens at 240-260°C. An a,p,(3-trifluorostyrene can be polymerized by free-radical mechanism to yield an amorphous polymer that softens at 240°C [290], Ring-substituted styrenes apparently polymerize similarly to styrene. Isotactic poly(o-fluorostyrene) melts at 265°C. It forms by polymerization with Ziegler-Natta catalysts [291]. The meta analog, however, polymerized under the same conditions yields an amorphous material [291]. 

Ready, T. E. Chien, J. C. W. Rausch, M. D. AUcyl-substituted indenyl titanium precursors for syndiospecific Ziegler-Natta polymerization of styrene. J. Organomet. Chem. 1996, 519, 21-28. 

It is known that both the isotactic and syndiotactic polymerizations of propylene with Ziegler-Natta catalysts occur by the cis opening of the double bond. Figure 4.1 shows the relationship between two kinds of copolymers obtained from deuterium-substituted styrene monomer and the conformation of their vicinal protons. 

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