MODULI OF MODEL ELASTOMERIC NETWORKS PREPARED FROM POLYMER-CHAINS HAVING A HIGH PLATEAU MODULUS, AND THEIR INTERPRETATION IN TERMS OF THE CONSTRAINED-CHAIN MODEL

High-molecular weight polybutadiene chains having approximately 47% cis-1,4 units and 45% trans-1,4 units were crosslinked through their carbon-carbon double bonds using p-bis(dimethylsilyl)benzene as crosslinking agent and chloroplatinic acid as catalyst. This particular polymer was chosen because the high plateau modulus it exhibits in the uncrosslinked state is taken to indicate large numbers of chain entanglements, and stress-strain measurements on such networks have frequently been interpreted with the assumption that the trapping of such entanglements during crosslinking should contribute significantly to their moduli. It is shown in the present investigation that such results are equally well interpreted in terms of the new constrained-chain theory of rubbery elasticity.