Network characterisation of end-linked poly(dimethylsiloxane) by ¹H-NMR-spin-spin relaxation

Summary

Above the glass transition temperature ¹H-NMR-spinspin relaxation curves of elastomers usually consist of two main components, a Gauss-like decay and a longer exponential decay. They can be attributed to inter-crosslink chains and free dangling chain ends, respectively, in accordance with basic ideas of the dynamics of polymer chains. By using an increasing amount of end-linking agent during the network synthesis of poly(dimethyl siloxane), the portion of the long decay is considerably reduced while the shape and the decay times remain approximately constant. This gives experimental evidence of the common classification of the decay components for the first time. Finally, the theoretical model for network dynamics used, which includes common phantom network properties and a concept of two independent motion scales, provides two mean correlation times and an average molecular mass of inter-crosslink chains.