Modulus of Polybutadiene Networks Made by Hydrosilation Cross-Linking

In this work we studied the effect of the topological interactions between polymer chains by measuring the small deformation modulus of polybutadiene networks. The networks were prepared by linking pendant double bonds (vinyls) on the polybutadiene with p-bis(dimethylsilyl)benzene catalized by platinum(II). Model reaction studies with a hexene and hexadiene mixture and a low molecular weight polybutadiene showed that this cross-linking reaction is complete and free of side reactions when the pendant double bonds are in excess. With silane in excess the backbone double bonds also react. Two monodisperse polybutadienes with different vinyl content and plateau moduli were linked with the same reaction. The small strain modulus measurements for the networks were better explained by including the effect of topological interactions along the contour of the network chains. The effect of interactions on the junction points was smaller that found by Dossin and Graessley for polybutadienes cross-linked by radiation.