The paper describes preparation and properties of butadiene‐pentadiene copolymers obtained with homogeneous systems prepared from Al(C2H5)Cl alcl and vanadium trichloride tetrahydrofuranate or vanadium triacetylacetonate, respectively. A brief examination of the catalyst forming reaction is included. Copolymers of every composition can be obtained. The influence of time and temperature of aging of the catalyst on copolymer yield is reported. The copolymers are richer in pentadiene than the corresponding monomer mixtures. Irrespective of the copolymer composition the butadiene units are all trans‐1,4 and the pentadiene units are partly trans‐1,4 and partly 1,2. The transition (Tt) and melting temperatures (Tm) of the copolymers decrease with increasing C5 content. Copolymers constituted of about 23 mole‐% C5 have Tm near 20°C. The latter copolymers give, after vulcanization, good elastomers, which are able to crystallize under stretching. At room temperature, the now appearing crystallinity is characteristic of the modification of trans‐1,4 polybutadiene which is stable above 75°C.
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Porri et al. (1963) studied this question.