Etude comparée des propriétés mécaniques dynamiques des formes I et II du polybutène-1. Cinetique de transformation II → I

The behaviour of the molecular motion in synthetic cis- and trans-1,4-polyisoprenes was studied by nuclear magnetic resonance. The line-widths (ΔH_pp), second (M₂) and fourth moments (M₄) of the absorption curves were measured at 77, 4.2, and 1.3 K. The obtained values of ΔH_pp and M₂ for cis-polyisoprene indicate that the molecular motions are apparently not completely quenched at 77 K since there is a further increase in the values of M₂ and ΔH_pp when decreasing the temperature from 77 to 4.2 K. It was found also that the value of M₂ at 4.2 and 1.3 K (? 20 G²) was larger than the previously computed one for a rigid lattice (18.5 G²). The temperature dependence of M₂ and ΔH_pp for trans-polyisoprene is different from that for cis-polyisoprene. The values of M₂ are constant in the range from 77 to 1.3 K (? 19.5 G²), which suggests that the molecular motion is presumably stopped in this polymer already at 77 K.