ポリイソプレンのミクロ構造と諸性質との関係

概要

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To correlate the chemical structure and physical properties of polyisoprene, polyisoprenes were synthesized with anisole-butyl lithium system varying cis-content from 90 to 40% and keeping the average molecular weight and the distribution to be constants. The polymers were press-cured with dicumyl peroxide and the physical properties were measured to suggest the following conclusions; (1) Glass transition temperature was well correlated with the microstructures. (2) In transition region, the shape of relaxation modulus against time was much similar to each other and the difference was reflected on the glass temperature. (3) In rubbery region, the strage modulus was independent of the microstructure but depended on the density of cross linked chain. (4) The loss modulus and loss tangent were increased with the decrease of cis-content. (5) Assuming the shape of the relaxation spectra as Aθ-m, the constant, m, was increased with decrease of cis-content. (6) Tmax, at which the maximum elongation at break was observed, was shifted from 100° to-40°C by the chemical structure. (7) The back bone chain was stiffened mainly with 3, 4-structure. (8) Combining these facts with heat build-up, durability, extensibility and so on, high cis-polyisoprene would be more desirable than low cis-polymers for rubber products such as tires.
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