Vibrational Dynamics of a Chiral Smectic Liquid Crystal Undergoing Vitrification and Cold Crystallization

• Main Authors: Anna Drzewicz, Ewa Juszyńska-Gałązka, Wojciech Zając, Przemysław Kula
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Crystals
• Subjects: liquid crystals; Fourier transform infrared spectroscopy; vibrational dynamic; perturbation-correlation moving window two-dimensional analysis; two-dimensional correlation analysis; DFT calculations
• Online Access: https://www.mdpi.com/2073-4352/10/8/655

Vibrational dynamics in the glass transition and the cold crystallization process of (S)-4′-(1-methyloctyloxycarbonyl) biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-benzoate (3F7HPhH7) was studied by Fourier transform infrared spectroscopy (FTIR) during cooling/heating experimental runs. The measured spectra processing was supported by quantum chemical density functional theory (DFT) calculations (frequency assignments). The perturbation-correlation moving window two-dimensional analysis (PCMW2D) was performed to examine how the height of individual absorption bands change under with temperature. Two-dimensional correlation analysis (2D-COS) was used to detect freezing-in or activation of the stochastic movements during the vitrification and the cold crystallization processes. Upon cooling, the vitrification process involves freezing-in of the stochastic movements of ester groups. Upon heating, as the cold crystallization process begins, the first to respond are the vibrations of the C–O–C and C=O groups in the rigid core.