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Current issue   Ukr. J. Phys. 2014, Vol. 59, N 3, p.292-298
    Paper

Baran J.,1 Davydova N.A.2, Drozd M.1, Ponezha E.A.3, Reznichenko V.Ya.2

1 Institute of Low Temperature and Structure Research, PAS
(2, Okolna Str., Wroclaw, Poland)
2 Institute of Physics, Nat. Acad. of Sci. of Ukraine
(46, Prosp. Nauky, Kyiv 03680, Ukraine; e-mail: davydova@iop.kiev.ua)
3 Bogolyubov Institute for Theoretical Physics, Nat. Acad. of Sci. of Ukraine
(14b, Metrologichna Str., Kyiv 03680, Ukraine)

Nature of the Dynamic Crossover in Orthoterphenyl

Section: Solid matter
Language: English

Abstract: We have conducted the infrared spectroscopic study and differential scanning calorimetry measurements (DSC) on orthoterphenyl (OTP), aiming to explore the physical nature of the dynamic crossover at 1.2 Tg found in variety experiments on OTP. We have obtained that, at T ≤ 1.2Tg(∼290 K) in the supercooled liquid OTP, the crystal nuclei appear and are absent at higher temperatures. These results suggest that the origin of the dynamic crossover at 1.2Tg is related to the formation of fluctuating nuclei in the supercooled liquid, as a temperature of 1.2Tg is approached. Therefore, we would expect that the appearance of the nuclei would change the molecular dynamics from individual to cooperative.

Key words: differential scanning calorimetry, infrared spectroscopy, glass transition, nucleation, orthoterphenyl, supercooled liquids.