Dynamics of polybutadiene reinforced with unsaturated carboxylate studied by muon spin relaxation (μSR)

Muon spin relaxation (μSR) measurements were performed to investigate the dynamics of polybutadiene (PB) reinforced by zinc diacrylate (ZDA). The spin relaxation rate was found to be almost independent of temperature below the glass transition temperature Tg, while it increased monotonically with temperature above Tg. In addition, the spin relaxation rate for PB including 14 vol% ZDA, which has a higher elastic modulus, was slower than that of PB without ZDA. Thus, μSR can clearly distinguish the dynamics of PB in these two samples, with the spin relaxations mainly caused by the so-called α-process (above Tg) and fast β-process (below Tg). To examine this scenario in detail, we performed μSR experiments as a function of longitudinal magnetic field (LF). The motional relaxation rate for PB was independent of temperature below Tg, confirming that the spin relaxation is mainly induced by the fast β-process. The α-process above Tg was also confirmed based on the Vogel-Fulcher-type temperature dependence, and the motional relaxation rate in the α-process was decreased by ZDA aggregates. These findings clearly show that μSR measurements provide useful information on the dynamics in complex polymer systems.

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