TY - JOUR

T1 - Polymorphic transformations of C 26H 54 and C 28H 58 n-paraffins as typical rotator substances

AU - Gnatyuk, I. I.

AU - Platonova, N. V.

AU - Puchkovskaya, G. A.

AU - Kotelnikova, E. N.

AU - Filatov, S. K.

AU - Baran, J.

AU - Drozd, M.

PY - 2007/7/1

Y1 - 2007/7/1

N2 - Thermal deformations and polymorphic transformations of two long-chain evennumbered normal paraffins C 26H 54 and C 28H 58 were studied by thermal X-ray diffraction (temperature step is tenths of a degree), infrared spectroscopy (temperature step is 1-5°), and differential scanning calorimetry (temperature step is 2° in a sample heating melt cooling mode. The samples are characterized by high homologous purity (99.0%) and belong to so-called "boundary" n-paraffins. The starting C 26H 54 n-paraffin sample is a triclinic modification at room temperature (Tc cryst). When quickly cooled, the melt crystallizes as the triclinic Tc cryst and monoclinic monolayer 1M cryst forms (two-phase mixture Tc cryst + 1M cryst). The starting C 28H 58 n-paraffin sample is a double-layer monoclinic modification 2M cryst at room temperature. Crystallization from hexane or slow cooling of a melt leads to a monolayer monoclinic form 1M cryst. Thermal deformations and temperature ranges of existence of the crystalline forms (Tc cryst, 1M cryst, and 2M cryst), low-temperature rotator crystalline orthorhombic form (Or rot.1), and high-temperature rotator crystalline hexagonal (H rot.2) phases of these n-paraffins were evaluated from changes in their diffraction patterns and unit cell parameters. The molecular structure and the conformational composition of these n-paraffins in different states were found from their IR spectra. Differential scanning calorimetry (DSC) was used to determine the phase transition temperature. Thermal X-ray diffraction, IR, and DSC data agree well with one another.

AB - Thermal deformations and polymorphic transformations of two long-chain evennumbered normal paraffins C 26H 54 and C 28H 58 were studied by thermal X-ray diffraction (temperature step is tenths of a degree), infrared spectroscopy (temperature step is 1-5°), and differential scanning calorimetry (temperature step is 2° in a sample heating melt cooling mode. The samples are characterized by high homologous purity (99.0%) and belong to so-called "boundary" n-paraffins. The starting C 26H 54 n-paraffin sample is a triclinic modification at room temperature (Tc cryst). When quickly cooled, the melt crystallizes as the triclinic Tc cryst and monoclinic monolayer 1M cryst forms (two-phase mixture Tc cryst + 1M cryst). The starting C 28H 58 n-paraffin sample is a double-layer monoclinic modification 2M cryst at room temperature. Crystallization from hexane or slow cooling of a melt leads to a monolayer monoclinic form 1M cryst. Thermal deformations and temperature ranges of existence of the crystalline forms (Tc cryst, 1M cryst, and 2M cryst), low-temperature rotator crystalline orthorhombic form (Or rot.1), and high-temperature rotator crystalline hexagonal (H rot.2) phases of these n-paraffins were evaluated from changes in their diffraction patterns and unit cell parameters. The molecular structure and the conformational composition of these n-paraffins in different states were found from their IR spectra. Differential scanning calorimetry (DSC) was used to determine the phase transition temperature. Thermal X-ray diffraction, IR, and DSC data agree well with one another.

KW - Crystalline and rotator crystalline states

KW - Differential scanning calorimetry

KW - IR spectroscopy

KW - Normal even long-chain n-paraffins

KW - Phase transformations

KW - Thermal X-ray diffraction

UR - http://www.scopus.com/inward/record.url?scp=35648958689&partnerID=8YFLogxK

U2 - 10.1007/s10947-007-0099-4

DO - 10.1007/s10947-007-0099-4

M3 - Article

AN - SCOPUS:35648958689

VL - 48

SP - 654

EP - 665

JO - Journal of Structural Chemistry

JF - Journal of Structural Chemistry

SN - 0022-4766

IS - 4

ER -