K. Saalwächter, M. Klüppel, H. Luo, H Schneider.
Chain Order in Filled SBR Elastomers: A Proton Multiple-Quantum NMR Study.
Appl. Magn. Reson. 27, 401-417 (2004).
A series of cross-linked SBR rubbers filled with different amounts of carbon
black and silica is investigated by proton multiple-quantum NMR. The method
yields reliable information on residual dipolar couplings and their
distribution, which in turn are related to local chain order and the effective
cross link density in these systems. Fundamental differences between the
response of a linear precursor, which undergoes reptational motion, and
vulcanized SBR are discussed. For the latter, it is found that the average chain
order parameter as well as its distribution does not change significantly with
the amount and the type of filler. This is in surprising contrast to recent
results from Hahn-echo relaxometry applied to the same samples, which indicated
a significant filler effect on the cross link density.