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It is shown that polyisoprene synthesised in the presence of a catalyst based on an alcohol solvate of gadolinium chloride is similar in molecular characteristics to ‘neodymium’ polyisoprene produced using a similar catalyst. A considerable advantage of the ‘gadolinium’ polymer is the high homogeneity of its microstructure. Specimens of ‘gadolinium’ polyisoprene were synthesised in the Mooney viscosity range 60-90, characterised by the complete absence of gel fraction, in which the content of cis-1,4-units amounts to 98.7-99.1%. The physicomechanical properties of the ‘gadolinium’ polyisoprene were investigated. These properties were compared with the properties of a ‘neodymium’ isoprene rubber (industrial SKI-5PM rubber). It was established that the more regular microstructure of the ‘gadolinium’ polyisoprene by comparison with the ‘neodymium’ polyisoprene is manifested by higher strength and dynamic indices of the rubbers. The resistance to repeated elongation for industrial specimen SKI-5PM with a Mooney viscosity of 78.8 approaches 81 000 cycles, whereas for the ‘gadolinium’ specimen with a similar Mooney viscosity this index reaches 94 000 cycles, and for the ‘gadolinium’ polymer with a Mooney viscosity of 85 and 90 the resistance to repeated elongation exceeds 100 000 cycles. Advantages of the ‘gadolinium’ polyisoprene in terms of tear strength, nominal tensile stress, etc., are also noted.

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