Butadiene‐propylene alternating copolymers

A general account is given of the alternating copolymer of butadiene with propylene. The copolymerization can be carried out at low temperature in the presence of V‐ or Ti‐based, modified Ziegler‐Natta catalyst which is prepared at a very low temperature (‐70°C). The structure of the copolymer was investigated by ozonolysis and 220 MHz NMR spectroscopy. A high degree of alternation, more than 97%, has been confirmed. For copolymerization a mechanism involving alternating coordination of olefin and diolefin is proposed. Finally, physical properties such as green strength, dynamic moduli, processability, etc., are illustrated in an application as a synthetic elastomer. The copolymer exhibits high strength and elongation at break perhaps because of induced orientation. The stress‐strain behavior is discussed in terms of a theory of elasticity and it is concluded that the alternating copolymer may have a flexible chain in spite of the trans‐structure of the butadiene unit.