Physical Chemistry of the Phase Transition at 19°C in Polytetrafluoroethylene as Probed by IR Spectroscopy

The spectra of the polytetrafluoroethylene crystal lattice at temperatures close to the solid-state phase transition (PT) in this partially crystalline polymer were measured and analyzed. The increased sensitivity of the spectral parameters of the bands of external translational and rotational modes in these spectra to crystal effects made it possible to assign the PT at 292 K (19°C) not only to structural reorganization, but also to subsequent orientational disordering of the crystal lattice at 304 K.