Temperature Dependence of the Structural Relaxation Time in Equilibrium below the Nominal Tg: Results from Freestanding Polymer Films

摘要: When the thickness is reduced to nanometer scale, freestanding high molecular weight polymer thin films undergo large reduction of degree cooperativity and coupling parameter n in Coupling Model (CM). The finite-size effect together with surfaces mobility make α-relaxation time nanoconfinement, ταnano(T), much shorter than ταbulk(T) bulk. consequence avoidance vitrification at below bulk glass transition temperature, Tgbulk, on cooling, film remains thermodynamic equilibrium temperatures Tgbulk. Molecular dynamics simulations have shown that specific volume same as glass-former temperatures. Extreme nanoconfinement renders total or almost removal α-relaxation, ταnano(T) becomes JG β-relaxation τβbulk(T) ...