The polymorphism of 1-heptadecanol (C 17 H 35 OH), 1-octadecanol (C 18 H 37 OH), 1-nonadecanol (C 19 H 39 OH), and 1-eicosanol (C 20 H 41 OH) has been studied by X-ray powder diffraction, differential scanning calorimetry (DSC), Raman scattering, and infrared spectroscopy (IR). At room-temperature two monoclinic forms, and γ, are observed. For the n-alkanols with an even number of carbons the stable form is γ, whereas is the stable form for the n-alkanols with an odd number of carbons. On heating, these phases transform to a monoclinic, rotator form R' IV at a few degrees below the melting point. A metastable form is obtained by quenching from the melt for 1-octadecanol and 1-eicosanol, which is isostructural with the -phase of the odd alkanols. Cell parameters, temperatures, and enthalpies of the transitions are reported.

bode, et al.. Polymorphism of even saturated carboxylic acids from n-decanoic to n-eicosanoic acid.The polymorphism of normal saturated even carboxylic acids from n decanoic to n eicosanoic acid is discussed. Seven crystal modifications, including polymorphs and polytypes, were identified and fully characterized by the combination of calorimetric measurements (DSC) at atmospheric and high pressures, X ray powder diffraction, FT IR spectroscopy and scanning electron microscopy (SEM). All seven crystal forms, including polymorphs and polytypes, are observed at room temperature. Forms A 2 and A super are triclinic, form C is monoclinic and forms E and B show both a monoclinic and an orthorhombic polytype. The triclinic modifications A 2 and A super predominate for acids up to n tetradecanoic acid (C 14 H 27 O 2 H). The orthorhombic and the monoclinic forms predominate for acids from n hexadecanoic (C 16 H 31 O 2 H) up to n eicosanoic acid (C 20 H 39 O 2 H). When the temperature is increased, all the crystal modifications transform irreversibly to the C form. In the first part of this paper, cell parameters for the different forms are given, the observed temperatures and enthalpies of the transitions are reported and the stability of the different forms is discussed. In the second part, we state the main contribution of each technique for the identification and interpretation of the polymorphism of even numbered carboxylic acids.

The experimental systems considered in this paper are normal alkanes, in the range from octane to octacosane; and their binary mixtures {(1-x) mol of CnH2n+2 + x mol of Cn′H2n′+2}, with n′ > n, and ∆n ) n′ -n taking the values 1 and 2. The alkanes and their mixtures have a rich, complex polymorphic nature, for the description of which a distinction is made between a high-temperature and a low-temperature domain. The high-temperature domain is occupied by rotator phases, and the low-temperature domain by a variety of mixed crystalline phases, referred to as the "ordered" phases. Experimental phase diagram data for 19 binariessincluding 11 binaries for which original data are presentedsare used to give a uniform and coherent description of the phase relationships for the ensemble of alkane alloys.

Many physical properties (e.g., hardness, texture, rheology, and spreadability) of lipid-based products largely depend on the extent of crystallization and transformation of lipids, and their network formation. Therefore, many studies have focused on controlling the crystallization of lipids in order to determine the functionality of lipid crystals. Both internal and external factors greatly affect the processes of lipid crystallization. The most important internal factors are polymorphism, which depends on variation in fatty acid moieties, and the composition or blending of different lipid materials. Important external factors are thermal treatment, additives, application of shear, sonication, and pressure. This paper briefly reviews recent advances in research on these external factors. We discuss the results by considering the relationships between external factors and thermodynamics, as well as kinetic properties of the crystallization and transformation of polymorphic forms of lipid crystals.

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