Molecular mobility in the adsorption layer and chain orientation in strained poly(dimethylsiloxane) networks by 2H NMR

The molecular mobility at the elastomer/active filler interface is studied in Aerosil‐filled poly(dimethylsiloxane) networks. It is shown that in unstrained samples two regions of different local chain mobility can be distinguished, namely chain units in the adsorption layer and outside of it. The fraction of chain units with relatively low mobility in the adsorption layer is estimated. In a uniaxially strained sample, immobilization of chain units near the filler surface is observed at temperatures up to 20 K above the melting temperature of an unstrained sample. The network structure of unfilled and filled networks is probed by analysis of the quadrupolar splitting in 2H solid‐echo spectra of uniaxially strained samples. The local chain order at a given elongation is larger by a factor of 1,5–2 in the filler system. This is interpreted in terms of an increased number of effective cross‐links and the differences between macroscopic and microscopic strains.