Compendium of the most significant studies with reference to properties, intake, effects.

Cho, S. Y., & Fogler, H. S. (1999). Efforts on solving the problem of paraffin deposit. I: using oil-soluble inhibitors. Journal of Industrial and Engineering Chemistry, 5(2), 123-127.

Abstract. Two paraffin carbonate materials, Jolliet wax from crude oil and hexatriacontone, were used in this study to test the effectiveness of different wax inhibitor candidates, including arachidyl alcohol, behenic acid, poly(ethylene vinyl acetate) and poly(1-octadecene maleic anhydride). It was found that both natural and manufactured paraffin wax could not be easily stabilized in the organic media by these chemicals. From the experimental result, it is proposed that effective paraffin inhibitors require a sufficiently long aliphatic chain structure to form strong van der Waals attractions to paraffin molecules to prevent or modify their crystallization. These long aliphatic chain of inhibitors may result in the instability of inhibitors. Polymeric molecules such as poly ethylene vinyl acetate) can slightly reduce the precipitation temperature of paraffin wax materials.

Cooper LL, Oliver JE, De Vilbiss ED, Doss RP. Lipid composition of the extracellular matrix of Botrytis cinerea germlings. Phytochemistry. 2000 Jan;53(2):293-8. doi: 10.1016/s0031-9422(99)00495-1. 

Abstract. Six simple lipid classes (mono-, di- and tri-acylglycerols, free fatty acids, free fatty alcohols and wax esters) were identified by TLC in the extracellular matrix of Botrytis cinerea germlings and the molecular components of each class were characterized using GC-MS. The relative amounts of fatty acids and fatty alcohols within each lipid class were determined by GC-FID. Over all the lipid classes, the most abundant saturated fatty acids were palmitic (ca. 30%) and stearic acid (ca. 22%). Palmitoleic and oleic acids made up ca. 21% and 24% (respectively) of the free fatty acids, while erucic (ca. 4.1%) and linoleic (ca. 3.6%) acids were the most abundant unsaturated fatty acids in the acylglycerides. The acylglycerides also contained almost 35% long chain fatty acids (C20:0 to C28:0). Six fatty acids were identified which had odd-numbered carbon chain lengths (C15:0, C17:0, C19:0, C21:0, C23:0 and C25:0). Of these, pentacosanoic acid made up almost 14% of the fatty acids in the acylglycerides. Three methyl-branched chain fatty acids, namely isopalmitic, isoheptadecanoic and anteisopalmitic, were identified in the ECM, all in small amounts. Of the fatty alcohols identified, only palmityl and stearyl alcohols were found in the free form (ca. 57% and 43%, respectively) but arachidyl alcohol (ca. 47%) and 1-octacosanol (ca. 30%) were the most abundant fatty alcohols found in the wax ester fraction.

Iwai, Y., Koga, Y., & Arai, Y. (1996). Monte Carlo simulation of n-paraffins and higher alcohols in supercritical carbon dioxide. Fluid phase equilibria, 116(1-2), 267-274.

Abstract. Monte Carlo simulation has been applied to calculate the static properties of n-paraffins; octacosane (C28H58) and triacontane (C30H62) and higher alcohols; cetyl alcohol (C16H33OH), stearyl alcohol (C18H37OH) and arachidyl alcohol (C20H41OH) in supercritical carbon dioxide at 308.2 K. Carbon dioxide was treated as single site molecule for simplification, while chain molecules (n-paraffins and higher alcohols) were approximated as many sites molecules. The residual chemical potential was calculated by the isothermal-isobaric Kirkwood method. It was shown that the solubilities (solid-gas equilibria) of n-paraffins and higher alcohols in supercritical carbon dioxide can be calculated quantitatively by introducing only one intermolecular parameter between unlike sites. The calculated results of mean-square end-to-end separations of n-paraffins increases with the pressure both in supercritical carbon dioxide and in supercritical ethane. The mean-square end-to-end separations of n-paraffins in supercritical carbon dioxide are shorter than those in supercritical ethane. Furthermore, the first peaks of the radial distribution functions of carbon dioxide for n-paraffins are lower than those of ethane for n-paraffins. These facts mean that supercritical carbon dioxide acts to n-paraffins as a poor solvent compared with supercritical ethane. The radial distribution functions of carbon dioxide for higher alcohols imply that carbon dioxide tends to cluster around hydroxyl group.

Dasgupta, A., & Macaulay, R. (1995). Microwave-induced rapid synthesis of 4-carbethoxyhexafluorobutyryl derivatives of fatty alcohols—a novel derivative for gas chromatography-chemical ionization mass spectrometric study. Journal of Chromatography A, 695(1), 136-141.

Abstract. Structural analyses of fatty alcohols are usually performed as acetate, trifluoroacetate or trimethylsilyl derivatives which produce characteristic molecular ions at m/z < 400. We describe a new derivatization technique of fatty alcohol using 4-carbethoxyhexafluorobutyryl chloride. The derivatization reaction requires either 30 min of incubation of the reaction mixture at 60°C, or 4 min of microwave irradiation using 240 W power. The yields of the derivatives were quantitative under both heating condition and microwave irradiation. The 4-carbethoxy hexafluorobutyryl derivatives of fatty alcohols produce characteristic protonated molecular ion peaks in the range of m/z 493 (cetyl alcohol) to m/z 549 (arachidyl alcohol) in the chemical ionization mode using methane as reagent gas. The molecular ion peaks were 54 u more than the conventional heptafluorobutyryl derivatives of fatty alcohols which can also be prepared by microwave irradiation in 3 min (240 W). The new derivatives are less volatile than the conventional heptafluorobutyryl derivatives.

Lukić, M., Pantelić, I., Daniels, R., Mueller-Goymann, C., Savić, M., & Savić, S. (2013). Moisturizing emulsion systems based on the novel long-chain alkyl polyglucoside emulsifier The contribution of thermoanalytical methods to the formulation development. Journal of Thermal Analysis and Calorimetry, 111(3), 2045-2057.

Abstract. Mesomorphic behavior of the novel long-chain alkyl polyglucoside emulsifier comprising arachidyl alcohol (C20), behenyl alcohol (C22), and arachidyl glucoside was investigated in order to determine the prevalent stabilization mechanism and moisturizing capacity of emulsion systems based on it. For this to be accomplished thermoanalytical methods (differential scanning calorimetry and thermogravimetric analysis) coupled with microscopy, rheological, X-ray diffraction methods and a short-term in vivo study of skin hydration level were performed. Obtained results have proved that C20/C22 alkyl polyglucoside mixed emulsifier is able to provide the synergism between the two main types of lamellar phases, the liquid-crystalline (Lα), and the gel crystalline (Lβ) one, building the emulsion systems of different stability and performance. Formation of lamellar structures influenced for more than one half of water within the system to be entrapped. Conducted investigation of hydration potential in real-time conditions provided valuable information on the investigated emulsion vehicles’ moisturizing potential as well as their contribution to the skin barrier improvement. Therefore, it could be expected that emulsions based on this alkyl polyglucoside emulsifier could influence the delivery of active ingredients of both the lipophilic and hydrophilic type. The employment of thermoanalytical methods in our work suggests the possibility for thermal methods to be used more frequently in the characterization of both the novel raw materials and the belonging emulsion systems.

Leiske, D. L., Rosenfeld, L., Monteux, C., Senchyna, M., Ketelson, H. A., & Fuller, G. G. (2011). Non-ideality in the Dynamic Wetting Behavior of Meibum Covered Droplets. Investigative Ophthalmology & Visual Science, 52(14), 3733-3733.

Abstract. Purpose:Lipid layer spreading and tear film dewetting are important variables influencing tear film stability. The viscoelasticity of meibomian lipids (ML) may govern tear film wetting dynamics. Furthermore, changes in ML composition that may accompany dry eye could alter melt temperature and viscoelastic properties, which may ultimately influence tear film spreading and dewetting. The purpose of this work was to gain insight into the effects of surface elasticity on the dynamic wetting of ML droplets....Results: : For a single plate velocity, the contact angles of AA covered droplets were constant. The equilibrium contact angle increased with increasing plate velocity such that the results followed the Cox-Voinov law, which predicts ideal behavior in Newtonian systems with constant surface tension. Although the contact angle was constant for ML covered droplets above 5 mm/s, the contact angle did not follow the Cox-Voinov law. At low velocities 0.01-0.5 mm/s we observed a stick/slip regime of the contact line where the contact angle would gradually increase then suddenly drop at regular intervals (period of ~2mm). Conclusions: : As the dynamic wetting of AA covered droplets followed predicted behavior, we conclude that insoluble surfactants do not necessarily result in non-ideality. We attribute the stick/slip and irregular behavior at high velocities of ML covered drops to interfacial elasticity. This deviation could influence lipid layer spreading, as well as tear film dewetting in dry eye patients.

Rosenfeld, L., & Fuller, G. G. (2012). Consequences of interfacial viscoelasticity on thin film stability. Langmuir, 28(40), 14238-14244.

Abstract. The phenomenon of dewetting is frequently observed in our everyday life. It is of central importance in many technological applications as well as in a variety of physical and biological systems. The presence of nonsoluble surfactants at an air/liquid interface may affect the dewetting properties of the aqueous layer. An important example is the tear film, which comprises an aqueous layer covered with a ∼100-nm-thick blanket of lipids, known as the meibomian lipids. Interfacial rheological measurements of meibomian lipids reveal that these films are remarkably viscoelastic. Tear film dewetting is of central importance to understanding tear film stability. To better understand the role of surface viscoelasticity in tear film stability, we have developed a methodology to systematically control interfacial rheology of thin aqueous layers at the onset of dewetting events. The apparatus allows control over the surface pressure of the monolayer, which is a key feature since this variable controls the surface viscoelasticity. Three insoluble monolayer materials were used: Newtonian arachidyl alcohol (AA), DPPC, a phospholipid that is slightly viscoelastic, and meibum, which produces a strongly viscoelastic monolayer. It is reported that monolayers of viscoelastic surfactants are able to stabilize thin films against spontaneous dewetting. As the surface pressure of these layers is increased, their effectiveness is enhanced. Moreover, these surfactants are able to reduce the critical film thickness for dewetting. Meibum is particularly effective in stabilizing thin films. Our results suggest that the meibomian lipids play a vital role in maintaining tear film stability in addition to suppressing evaporation.

Yamamoto, M., Iwai, Y., Nakajima, T., Tanabe, D., & Arai, Y. (2000). Correlation of solubilities and entrainer effects for fatty acids and higher alcohols in supercritical carbon dioxide using SRK equation of state with association model. Journal of chemical engineering of Japan, 33(3), 538-544.

Abstract. Solubilities of fatty acids (myristic acid, palmitic acid and stearic acid) and higher alcohols (cetyl alcohol, stearyl alcohol and arachidyl alcohol) in supercritical CO2, and the entrainer effect (ethanol or octane) on their solubilities, are correlated by the Soave-Redlich-Kwong equation of state with an association model. It is assumed that the system consists of supercritical CO2, solute monomer, solute dimer, hydrogen bonding species between solute monomer and entrainer, and entrainer. The mole fractions of these species are determined by the equilibrium constants for dimerization of palmitic acid, and those for hydrogen bonding species between palmitic acid and ethanol obtained from FTIR spectroscopic study. The calculated results agreed with the experimental data.

Pardeike, J., Schwabe, K., & Müller, R. H. (2010). Influence of nanostructured lipid carriers (NLC) on the physical properties of the Cutanova Nanorepair Q10 cream and the in vivo skin hydration effect. International journal of pharmaceutics, 396(1-2), 166-173.

Abstract. Cutanvoa Nanorepair Q10 cream, the first NLC containing cosmetical product introduced to the market in October 2005, was compared to an identical o/w cream without NLC with regards to particle size, melting behaviour, rheological properties and the in vivo effect on skin hydration. The consistency, the spreadability on the skin and the subjective feeling of increase in skin hydration were evaluated using a standardized questionnaire, and compared to hydration data measured. Furthermore, it was shown by epicutaneous patch test that Cutanova Nanorepair Q10 cream has no irritating effects on the skin. By laser diffraction (LD) and differential scanning calorimetry (DSC) measurements it could be shown that NLC are physically stable in Cutanova Nanorepair Q10 cream. After 7 days application of Cutanova Nanorepair Q10 cream and NLC negative control cream an increase in skin hydration could be objectively confirmed by measurements in vivo. From day 28 on the skin hydration measured in the test areas of Cutanova Nanorepair Q10 cream was significantly higher than the skin hydration in the test areas of the NLC negative control cream (p = 0.05). The subjective feeling of increase in skin hydration was also rated from the volunteers as superior for Cutanova Nanorepair Q10 cream. The rheological properties of Cutanova Nanorepair Q10 cream contributed to a better subjective impression of consistency and spreadability on the skin than found for NLC negative control cream.

Olson, D. J., & Fuller, G. G. (2000). Contraction and expansion flows of Langmuir monolayers. Journal of non-newtonian fluid mechanics, 89(1-2), 187-207.

Abstract. Langmuir monolayers consist of amphiphilic molecules at the air–water interface and can be modeled as two-dimensional fluids. We have performed 4 : 1 contraction and 4 : 1 expansion flows on arachidyl alcohol, a Newtonian monolayer, and on PODMA [poly(octadecyl methacrylate)], a non-Newtonian monolayer. Arachidyl alcohol shows no vortices in contraction flow, but exhibits very large inertial vortices in expansion flow. In contrast, during contraction flow PODMA exhibits large vortices that have little or no growth as a function of flow rate. The elasticity of PODMA tends to diminish the inertial vortices in expansion flow as a result of `die swell'. Normal stresses accumulated in the channel shear flow cause the fluid to expand into the downstream channel, pushing the vortices into the salient corner. These results are in qualitative agreement with planar contraction and expansion experiments performed on three-dimensional fluids. This correspondence in results between two-dimensional and three-dimensional fluids is encouraging because it allows one to predict the flow behavior of Langmuir monolayers based on previous results for three-dimensional polymers and demonstrates that extensional and nonlinear rheological behavior are important in these systems.

Takiguchi, H., Iida, K., Ueno, S., Yano, J., & Sato, K. (1998). Heterogeneous nucleation of n-alcohol crystals from solution assisted by vapor-deposited thin films of fatty acids. Journal of crystal growth, 193(4), 641-647.

Abstract. Solvent crystallization of long-chain n-alcohol crystals (hereafter referred to as guest crystals), which was accelerated in the presence of vapor-deposited thin films of long-chain fatty acids (host films) in slightly supersaturated decane solutions, was observed in situ. Fatty acids having an even number of carbon atoms (nc), of 18–24, and n-alcohol molecules having an even nc, of 18–22, were employed as the host and guest materials, respectively. It was confirmed that the host and guest materials constructed immiscible eutectic phases in bulk solids in all the combinations examined. Supersaturation of the solution was set so low that spontaneous solvent crystallization was not observed for several hours in the absence of the host thin films. The following results were obtained: (a) The rates of nucleation of guest crystals was markedly higher in the presence of host films, (b) acceleration of nucleation was observed only when the nc values of the host films were the same as or longer by 2 than those of the guest solutes, (c) the molecular orientation, either normal or lateral, with respect to the substrates of the host films was preserved in the newly crystallized guest crystals, and (d) polymorphic matching between host and guest materials was observed. These results indicate that heterogeneous nucleation having the characteristics of van der Waals forces was operative at the thin film/solution interface.

Handelman, G. J. (1999). High-performance liquid chromatography analysis of cholesterol linoleate hydroperoxide in oxidized low density lipoproteins: calibration by conjugated diene internal standard. In Methods in enzymology (Vol. 300, pp. 43-50). Academic Press.

Abstract. The cholesterol linoleate hydroperoxides formed in LDL after oxidant stress are measured by HPLC, with UV detection at 234 nm. Calibration is performed with a conjugated diene internal standard. This internal standard is synthesized by the transesterification of the methyl ester of conjugated diene linoleic acid with a long-chain alochol, such as arachidyl alcohol (C20). Different long-chain alcohols can be used during the transesterification, to achieve internal standards with variable HPLC retention times. The method allows measurement of cholesterol linoleate hydroperoxide in LDL very early during attack with Cu2+ or other initiator, so that the kinetics of antioxidant loss and hydroperoxide formation can be concurrently monitored.