Scaling analysis and distribution of the rotational correlation times of a tracer in rubbery and glassy poly(vinyl acetate): An electron spin resonance investigation

We studied by ESR the rotational motion of a paramagnetic tracer (a deuterated N-15-enriched nitroxide) in poly(vinyl acetate) (PVAc). The reorientation of the tracer occurs via jumps of about 50 degrees with a heterogeneous distribution of correlation times. Depending on the temperature range, the average correlation time [tau] scales as the alpha, beta, and gamma relaxation times of PVAc, i.e., [tau] = C-i[tau](i), i = alpha, beta, gamma. On cooling, [tau] tracks the alpha relaxation to about the alpha-beta bifurcation temperature and then the beta relaxation down to the glass transition. In glassy PVAc [tau]/[tau] = C-gamma approximate to 1.