The τ-effective paradox revisited: an extended analysis of Kovacs’ volume recovery data on poly(vinyl acetate)☆

摘要: Abstract In 1964 Kovacs (Kovacs, AJ, Transition vitreuse dans les polymeres amorphes. Etude phenomenologique. Fortschr Hochpolym-Forsch 1964;3:394–507) published a paper in which he analyzed structural (volume) recovery data asymmetry of approach experiments. used parameter referred to as τ-effective (τeff) is defined terms the volume departure from equilibrium δ τeff−1=−1/δ dδ/dt. plots log(1/τeff) vs. observed an apparent paradox that values τeff did not converge same point approached zero (i.e. equilibrium). Hence mobility seemed path dependent. Also, was accompanied by spreading curves for up-jump experiments has come be known expansion gap. While it currently accepted itself does exist because will if measurements are made closer δ=0 (Kovacs’ estimates were small δ≈1.6×10−4), existence gap still subject dispute. This particularly relevant today recent models have claimed ‘success’ specifically predicted. Here we take 1964, unpublished his notebooks taken at time, well more obtained Institut Charles Sadron under tutelage late 1960s and early 1980s. We then examine them using several different statistical analyses test following hypothesis: value |δ|→1.6×10−4 temperature jump Ti T0 significantly Tj T0. The temperatures or can either greater less than If hypothesis rejected, τeff-paradox need rethought. accepted, argument reproduction important strengthened. Our analysis leads conclusion extensive set 40°C support gap, hence apparently paradoxical τeff, |δ|≥1.6×10−4. However, smaller |δ| appears no longer statistically and, fact, suggest |δ|→0 all converge. addition, 35°C do sufficient accuracy such duration those 40°C. Consequently readings time intervals this dramatically reduced error correlations.