Crystal structure and microstructure of cholesteryl oleyl carbonate

Area of Science:

• Crystallography
• Materials Science
• Solid-State Chemistry

Background:

• Cholesteryl esters are crucial in biological systems and materials science.
• Understanding the crystal structure of cholesteryl oleyl carbonate (COC) is key to its material properties.
• Previous studies have characterized similar cholesterol esters, providing a basis for comparison.

Purpose of the Study:

• To determine the crystal structure and microstructure of cholesteryl oleyl carbonate (COC).
• To analyze X-ray diffraction data for crystallite size, strain, and structural parameters.
• To compare the crystal structure of COC with structurally similar cholesterol esters like cholesteryl oleate (CO).

Main Methods:

• X-ray powder diffraction (XRD) was employed to collect diffraction data.
• Analysis involved refinement of TCH-pseudo-Voigt functions for isotropic effects.
• Refinement of multipolar functions (symmetrized cubic harmonics) was used for anisotropic effects.

Main Results:

• COC was found to have a primitive monoclinic crystal structure (space group Pc) with a type I monolayer.
• Unit cell parameters were determined: a=18.921±0.006Å, b=12.952±0.003Å, c=9.276±0.002Å, β=91.32±0.03°.
• Average crystallite size was 60nm, with micro-strain attributed to fatty chain disorder. COC structure is similar to CO, supporting a type I monolayer for COC.

Conclusions:

• The crystal structure of cholesteryl oleyl carbonate (COC) is primitive monoclinic, space group Pc, type I monolayer.
• COC exhibits structural similarities to cholesteryl oleate (CO), particularly in unit cell parameters and lamellar thickness.
• Binary mixtures of CO and COC can form induced smectic phases with lamellar thicknesses comparable to the pure components.