An Ultrastable Polymeric Glass: Amorphous Fluoropolymer with Extreme Fictive Temperature Reduction by Vacuum Pyrolysis

Vacuum pyrolysis deposition (VPD) has been used to create an ultrastable polymer glass having a fictive temperature T_f of as much as 57 K below the nominal glass transition temperature of the thermally rejuvenated polymer. Amorphous fluoropolymer films 300 to 700 nm thick were created by VPD followed by characterization of the thermal response using rapid-scanning chip calorimetry. The deposition was performed for substrates held at temperatures from 30.0 °C (303.2 K) to 116.7 °C (389.9 K) corresponding to approximately 0.75 to 0.97 times the limiting fictive temperature Tf^′ ≈ T_g of the same material determined by cooling then heating at 600 K/s. Consistent with literature observations for small molecules that are vapor deposited in similar conditions relative to the material T_g, large enthalpy overshoots are observed, typical of both highly aged and ultrastable glasses. The 57 K reduction in T_f for the VPD polymers is greater than prior reports for physical vapor deposition of small molecules to form ultrastable glasses as well as greater than the T_f reductions seen in ambers from 20 million to over 200 million years of age. The potential of using such materials to investigate systems extremely deep into the glassy condition is discussed.