Dynamic Behavior of Ultrastable Amorphous Teflon Films in the Deep Glassy Regime*

Recently, we have succeeded in producing high molecular weight ultra-stable amorphous Teflon films by vapor pyrolysis deposition method [Macromolecules 2017, 50, 4562−4574.]. The films produced here exhibited 57 K fictive temperature (T_f) reduction when the substrate temperature was between 0.75 to 0.97 times the glass transition temperature (T_g). This large T_f reduction gives an opportunity to investigate the dynamic behavior in the deep glassy regime. In the current work, we use this ultra-stable glass to study the relaxation behavior of the polymer in the temperature range between T_f and T_g where the glass has lower enthalpy and specific volume than the equilibrium system. The relaxation behavior of stable Teflon films was measured using the TTU nano bubble inflation technique following Struik’s protocol. The results are compared with Vogel-Fulcher-Tammann (VFT) dynamics determined above T_g. We found that there is a strong deviation from VFT dynamics in the upper bound regime.