title: Calorimetric and spectroscopic evidence of chain-melting in smectic E and smectic A phases of 4-alkyl-4'-isothiocyanatobiphenyl (nTCB).
abstract: To confirm the molten state of the alkyl chain in soft crystalline phase, smectic E (SmE) phase, thermodynamic and spectroscopic analyses were performed on 4-n-alkyl-4'-isothiocyanatobiphenyl (nTCB, n: the number of carbon atoms in the alkyl group). DSC results of 11TCB and 12TCB, having extra smectic A phase besides smectic E phase, show that their chain-length dependence of entropies of transition (Δ(trs)S) from the ordered crystalline (OC) phase to the SmE phase matches the trend found for nTCB (n = 4-10), while no chain-length dependence is observed in Δ(trs)S at the SmE-to-SmA and SmA-to-isotropic liquid (IL) phase transitions in 11TCB and 12TCB. Temperature dependences of FT-IR spectra of six compounds (n = 2, 3, 5, 8, 10, and 12) were recorded. The CH stretching modes of the chain exhibited more pronounced change at the transition from the OC to the SmE phase than at the transition from the SmE phase to the IL or SmA phase. These results indicate that the alkyl chain is molten in the SmE phase as in IL. The disordering process of nTCB molecules from the OC to IL via anisotropic mesophases is discussed in terms of entropy.
authors: Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
authors: Yasuhisa
authors: Y
authors: Yamamura
authors: Takuya
authors: T
authors: Adachi
authors: Takahito
authors: T
authors: Miyazawa
authors: Katsuya
authors: K
authors: Horiuchi
authors: Masato
authors: M
authors: Sumita
authors: Maria
authors: M
authors: Massalska-Arodź
authors: Stanisław
authors: S
authors: Urban
authors: Kazuya
authors: K
authors: Saito