Crystal structures of binary systems of saturated fatty acids

Abstract

Data on crystal lattices of t 3 different mixtures of the system palmitic acid:stearic acid (C16/C18) could be obtained by means of X-ray and electron diffraction. The modification occurring in all concentrations was found to be in conformity with the known74-or C-form of the pure components. It is characterized by the fact that, in mixtures with 95-60 mol % stearic acid, the shorter chained palmitic acid molecules may be incorporated in the crystal lattice of pure stearic acid without dimension c of the unit cell being changed. In concentration ranges of 50-20% C18molecules, one form of mixture which proves to be stable is characterized by constancy of nearly all unit cell parameters of various mixture ratios. From SP10 to SP0, the lattice constants of pure palmitic acid are mainly obtained. The occurrence of C18-molecules of up to 10% in the unit cell of palmitic acid results in a flight decrease of the angle fl by 1-2 ° and an enlargement of the distance to neighbored molecules.

Characterization of soybean protein concentrate—stearic acid/palmitic acid blend edible films

“…A similar effect was observed for gelatin‐hydrophobic compounds 17. After re‐heating crystallization seemed to be restricted to quite an extent as concluded from the shift to lower temperatures and reduced peak areas may be due to the restricted mobility of fatty acid chains in the absence of moisture which led to less perfect and stable crystals 35. This could also an indication solid‐solid transition between polymorphic forms of stearic acid induced by palmitic acid in quenched samples 35.…”

“…After re‐heating crystallization seemed to be restricted to quite an extent as concluded from the shift to lower temperatures and reduced peak areas may be due to the restricted mobility of fatty acid chains in the absence of moisture which led to less perfect and stable crystals 35. This could also an indication solid‐solid transition between polymorphic forms of stearic acid induced by palmitic acid in quenched samples 35. Calorimetric results agreed well with SEM observations and opacity results and confirmed that the dispersed phase in SA/PA‐SPC7 was mainly constituted by the un‐reacted fatty acids.…”

“…It is worth mentioning that the pattern of SA/PA blend superimposed that of pure SA with peaks at 2θ = 20.2, 21.5, and 24°, as well as by long spacing at 2θ = 6.64°, corresponding to pure stearic acid. This last peak was found at 2θ = 7.62° in pure PA. Frede and Precht35 stated that shorter chains of PA molecules could be incorporated in the crystal lattice of pure SA in mixtures containing 60–95%SA, without significant changes in the unit cell parameters. The XRD patterns of SA/PA blend‐containing SPC films are depicted in Figure 4(b).…”

Morphology of blends of self-assembling long-chain carbamate and stearic acid

“…However, none of the pure polymorphs of stearic acid exhibit such a strong reflection at d = 4.1 Å, as is observed in case of the blends of this study. Frede et al [16] observed a similar decrease in intensity at 40 Å and increase in intensity at 4.1 Å when they melt blended stearic acid with palmitic acid. However, they did not report the polymorphic transition observed in this study with the blends.…”

Phase and miscibility behavior of binary lipid systems

“…Long-chain carboxylic acids and esters of fatty acids have already been subjects of thermodynamic and structural analyses under different aspects [10][11][12][13][14][15][16][17][18]. In their solid states unbranched fatty acids from bilayers which are chiefly built up by hydrogen bonds between carboxyl groups [13,19,20].…”