Modification of the IR Spectra Shape in the 2000–2300 cm–1 Absorption Band upon the Aging of a Chemically Dehydrofluorinated Poly(vinylidene fluoride) Film

The stability of the atomic structure and physical and chemical properties of new materials is of crucial importance for their practical use. Long-term (about 120 000 min) and regular monitoring of the molecular structure of two samples of poly(vinylidene fluoride) (PVDF) film after its five-hour chemical dehydrofluorination and rinsing with ethanol are performed using infrared (IR) spectroscopy. The samples differed in low-pressure exposure duration before measurement. Changes in the absorption spectra of the stretching vibrations of triple carbon-carbon bonds are analyzed in the wave-number range of 2000–2300 cm–1. The initial PVDF film is transparent in this region, but, after dehydrofluorination, an absorption band of complex shape is observed in it. Visually, the band consists of three wide features with centers around 2050, 2100, and 2160 cm–1. The first and the second bands are absent immediately after synthesis, but, as the samples age, they appear and grow proportionally to each other and time intervals of rapid and slow growth, as well as a stabilization period, are observed.