Influence of magic angle spinning on T1H of SBR studied by solid state 1H NMR
نویسندگان
چکیده
We have investigated the influence of the high centrifugal pressure caused by fast magic-angle spinning (MAS) on the molecular motion of styrene–butadiene rubbers (SBR) filled with SiO2 (SBR/Si composite) though solid-state magic-angle spinning nuclear magnetic Resonance (1H MAS NMR) measurements. Because the 1H–1H dipolar interaction of elastomers is weak compared with that of glassy polymers, a narrower 1H linewidth is observed under fast MAS. The temperature dependence of the 1H spin-lattice relaxation time (T1 H) revealed that the T1 H minimum increases with the MAS rate. Furthermore, we observed a difference in the temperature dependence of T1 H between end-chain-modified SBR and normal (unmodified) SBR in the SBR/Si composites. The temperature dependence of T1 H is described by the Bloembergen–Purcell–Pound theory, with the assumption that the correlation time obeys the Williams–Landel–Ferry empirical theory. The fitting showed that the molecular motion does not change significantly until a MAS rate of 20 kHz, with the motional mode changing considerably at a MAS rate of 25 kHz. The motion of SBR in the unmodified SBR/Si composite was greatly affected by the fast MAS rates. Furthermore, the plot of the estimated centrifugal pressure versus the T1 H minimum resembled the stress–strain curve. This result enables the detection of macroscopic physical deformation by the microscopic parameter T1 H. Polymer Journal (2012) 44, 706–712; doi:10.1038/pj.2012.10; published online 7 March 2012
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