Monomeric friction coefficient of 1,2-polybutadienes

The monomeric friction coefficient has been determined for 1,2-polybutadienes from dynamic measurements in the transition zone. These values are, respectively, 7.59 × 10 −5, 3.09 × 10 −6, 5.25 × 10 −7 and 2.95 × 10 −9 g s −1 for 1,2-polybutadienes with vinyl contents of 91%, 76%, 53% and 14%. The structure-dependent behaviour of the monomeric friction coefficient has been discussed. 1,2-Polybutadienes with higher T g, i.e. with higher vinyl content, have a larger monomeric friction coefficient. The fact that the monomeric friction coefficient increases with increase in cross-sectional area of the polymeric chains describes the effect of chain flexibility on the monomeric friction coefficient. The quantitative relationship between the shortest relaxation time, τ A, and the tube diameter, d, in Doi-Edwards theory has also been reported: log τ A = −17.24+0.38 d.