Comments on “some evidence against the existence of the liquid‐liquid transition. IV. The temperature dependence of shear viscosity”

A formal definition of T LL as a function of M̄ n for polystyrene was prepared with literature T LL values from torsional braid analysis (TBA), differential scanning calorimetry (DSC), and zero‐shear melt viscosity η 0 . Data from six authors using anionically prepared PS and blends thereof were involved. The resultant linear least‐squares regression line, T LL (°C) = 148.5 − 11.487 × 10 4 M̄ [standard error in T LL (calculated) 4.056 K, correlation coefficient R 2 = 0.9534] is considered valid from M̄ n = 2000 to the entanglement molecular weight M c = 35,000. The “best” T LL values reported by Orbon and Plazek from double Arrhenius plots are well below this line for M̄ v = 47,000, 16,400, 3400, and above it for M̄ v = 1100. These best T LL values are artifacts arising from no or insufficient data points above or below T LL and/or too many data points near T g . The associated high enthalpies of activation which they report confirm this diagnosis. The fact that these artificial T LL values tend to disappear when checked by the three‐parameter Vogel equation, logη = log A + B exp[( T − T ∞ ) −1 ], has no relevance to the controversy concerning the existence and meaning of T LL . The claim by Orbon and Plazek that T LL values obtained by TBA, DSC, and melt viscosity are all artifacts of the individual methods by which they were obtained is inconsistent with the excellent master plot which they generate. Alternative plotting devices which reveal T LL > T g from η 0 vs. T −1 data, as developed by van Krevelen and Hoftyzer and by Utracki and Simha (not previously considered by either party), are reviewed. A statistical examination of the nature of the Vogel–Fulcher–Tammann–Hesse equation, based on synthetic data, is presented. Evidence for T LL in atactic polypropylene is offered based on published data by Plazek and Plazek. T LL is considered to possess both relaxational and quasiequilibrium attributes, just as T g does.