Longest relaxation time of linear polybutadiene chains trapped in rubber networks
Department of Solid State Physics, Risoe National
Laboratory, P.O. Box 49, DK-4000 Roskilde, Denmark
2 Department of Chemistry of the University of Copenhagen, Symbion, Fruebjergvej 3, DK-2100 Copenhagen, Denmark
Accepted: 6 June 1997
We have used dynamic-mechanical measurements to probe the long-time dynamics of linear, almost monodisperse polybutadiene chains in two media: a) their own melts and b) as trapped in our recently prepared elastomeric networks. The results are compared with the classical reptation-in-a-tube model of de Gennes and Doi and Edwards. Within experimental accuracy, the obtained experimental scaling of the longest relaxation time relative to the chain mass M (up to ) is the same in both media: with as against x=3 predicted by the "pure” reptation-in-a-tube model. However, the network data are well described in the range of molar masses , after correcting the reptation model for chain-end effects (in the form of contour length fluctuations). The for the chains trapped in a network were found to be 1.9–3.2 times longer than the of the respective melts. We present data on ten polybutadienes confined in two kinds of networks and covering the range of weight average molar masses –.
PACS: 61.41.+e – Polymers, elastomers, and plastics / 83.50.Fc – Linear viscoelasticity / 83.10.Nn – Polymer dynamics
© EDP Sciences, 1997