Nanostructured Oil in Cosmetic Paraffin Waxes - ACS Publications

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Nanostructured oil in cosmetic paraffin waxes Fan C. Wang, Yukihiro Miyazaki, and Alejandro G. Marangoni Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b00042 • Publication Date (Web): 28 Mar 2018 Downloaded from http://pubs.acs.org on March 29, 2018

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Crystal Growth & Design

Nanostructured oil in cosmetic paraffin waxes

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Fan C. Wang1, Yukihiro Miyazaki2, and Alejandro G Marangoni1*

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1. Department of Food Science, University of Guelph, Guelph, Canada

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2. Kao Corporation, Sumida-ku, Tokyo, Japan

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*Corresponding author: [email protected]

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Abstract

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This work examined the oil-binding behaviour of cosmetic paraffin wax – mineral oil systems

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using powder X-Ray diffraction (XRD), differential scanning calorimetry (DSC), and pulsed

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nuclear magnetic resonance (pNMR). Neat paraffin wax crystals and paraffin wax oleogels

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crystallized into the same polymorphic forms; however, the oleogels had a larger lamellar

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thickness and crystal domain size. This increase in lamellar size could indicate that the oil was

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structured in between individual wax crystalline lamellae (i.e., nanostructured oil). The amount

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of crystalline material determined by pNMR of wax oleogels increased with temperature below

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their melting point, because inter-lamellar nanostructured oil lost some mobility and displayed

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solid-like behaviour. These results provide experimental evidence for the existence of

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nanostructured oil, in support of simulation studies in the literature, and shed light into the oil-

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binding mechanism of some materials.

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Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Solid–liquid interactions are important in determining the oil-binding capacity of a

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material. Many theoretical studies have attempted to explain the oil-binding mechanism of

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materials using computer simulations. These studies have been performed on simple and

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complex fluids, such as n-alkanes in confined model pores1 and between parallel planes2–6, and

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oil between triglycerides (TAGs) nanoplatelets7,8. N-alkane polymers were found to change their

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chain conformation in confined space9,10, arrange into layered structures parallel to the surface,

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and display periodic oscillations corresponding to the length, width, and density of the polymer

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molecules11–13. No evidence was found for an immobile liquid layer near the solid substrate in

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these studies13. Similar to n-alkanes, liquid TAG oil was shown to arrange into layers parallel to

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the surfaces of solid TAG nanoplateletes and display a density gradient as a result of nano- phase

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separation7,8. Near the solid surface, oil molecules adsorb to the surface and display slower

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molecular diffusion, while the oil density increased when closer to the solid surface7,8.

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Experimental evidence in support of these simulation studies is scarce. In the current

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study, evidence for the existence of nanostructured confined oil between crystalline lamellae of

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cosmetic paraffin wax is provided, which could support results from simulation studies. We will

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further discuss the unique crystalline structure and swelling behaviour of cosmetic paraffin wax

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oleogels as well.

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Straight chain paraffin wax (Nippon Seiro Co., Ltd., Tokyo, Japan) used in this study is a

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crystalline solid mixture of hydrocarbons (C34–C40 alkanes) with a melting point of 72–74 °C

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obtained from petroleum. The oil phase used in wax oleogels is isotridecyl isononanoate, which

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is the ester of isotridecyl alcohol and isononanoic acid, and was purchased form Nisshin Oillio

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Group, Ltd. (Yokohama, Kanagawa, Japan). Polyethylene wax was purchased from New Phase

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Technologies (Sugar Land, Texas, USA), with a melting point of 83–90 °C. To prepare paraffin


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wax oleogel samples, wax-oil mixtures containing 0 to 100% paraffin wax were melted and

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mixed at 120 °C and then stored at 0 °C for 24 h to allow for crystallization. Samples were then

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kept at room temperature for at least 6 h before analysis. Wax and wax oleogel samples were

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studied using powder XRD, DSC, and pNMR, following the method used by Miyazaki and

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Marangoni14. Detailed experimental protocols are provided as supporting information.

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Figure 1. (a) XRD patterns of paraffin wax mixed with different amounts of oil, (b) lamellar

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thickness (d001) and crystal domain size (ξ) calculated form XRD data, (c) % increase in d001 and

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ξ of paraffin wax oleogel with different oil contents relative to neat paraffin wax crystals, and (d)

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correlation between % increase in d001 and % increase in ξ.

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Neat paraffin wax crystals and paraffin wax oleogels at various oil contents were all in the β´ polymorphic form, indicated by reflections at d=4.1Å and 3.7 Å calculated from wide


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angle diffraction (WAXD) peaks (Figure 1a). Small angle diffraction (SAXD) data of all samples

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suggest the presence of lamellar crystalline structures, with d-spacings appearing at 1:1/2:1/3

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corresponding to the main reflection and higher order reflections from the (001) crystallographic

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plane. SAXD peaks from higher order reflections (002, 003, etc.) were not observed from

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branched chain wax or straight chain polyethylene wax with a wider molecular size distribution

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(C20–C60 alkanes).

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The crystal domain size (ξ) of each sample was calculated following the Scherrer equation:

ξ=

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λ ×

Where K is the dimensionless shape factor (0.9), λ is the wavelength of the X-ray source

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(1.54 Å for copper anode source), FWHM is the full width half maximum of a Bragg’s peak

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(usually for the (001) plane), and is the angle of where a certain diffraction peak was obtained.

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Results show that even though neat paraffin wax crystals and paraffin wax oleogels are in

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the same polymorphic form, increases in lamellar thickness (d001) and domain size (ξ) with

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increasing oil content were observed (Figure 1b). The ratio between domain size and lamellar

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thickness can be used to estimate the number of lamellae per domain. The number of lamellae

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per domain was between 6.2 and 6.8 in all the samples, therefore we could assume that all

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samples have the same number of lamellae in the domain. The % increase in d001 and ξ of

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paraffin wax oleogels with various oil contents as compared to neat paraffin wax crystals was

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then calculated (Figure 1c). d001 increased by 11.0% while ξ increased by 21.0% upon increases


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in the oil content of wax oleogels from 0 to 80%. The increment in d001 is caused by swelling of

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paraffin wax lamellae in the presence of oil; while the increase in ξ is caused by both increases in

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d001 and the amount of inter-lamellar confined oil. A linear correlation suggested that the

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increase in ξ is 1.9 time of the increase in d001, as shown in Figure 1d. If no oil were structured

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between wax lamellae, the % increase in d001 and ξ should be the same.

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Figure 2. (a) Melting profiles of paraffin wax structuring 0 to 80% (w/w) of oil, and (b)

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Hildebrand plot of paraffin wax – oil system.

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The ideal solubility behaviour between paraffin wax and oil was also predicted using the Hildebrand equation15: =

Δ / 1/ 1/


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Where X represents the mole fraction of the higher melting component (paraffin wax in

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this case), ∆Hf is the enthalpy of melting for the higher melting component (in J/mol), R is the

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universal gas constant (8.314 J/mol･K), and Tm and Tb are the melting temperatures of the higher

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melting component and the blend (in K), respectively.

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The temperature and enthalpy of melting of each sample were determined using DSC

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(Figure2a). Results show that paraffin wax and mineral oil used in the concentration range of this

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study display ideal solubility in the liquid state, indicated by a linear correlation between lnX and

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1/Tb, as shown in Figure 2b16.

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Figure 3. Amount of crystalline material determined as the solid fat content (SFC) of oil

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structured with (a) 20% wt. paraffin wax (n=4, error bars are all smaller than the symbols), and

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(b) 20% (w/w). wax that contains a blend of 90% paraffin wax and 10% straight chain

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polyethylene wax (n=2, error bars are all smaller than the symbols).


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106 Upon heating from 0 to 35˚ C, still below the melting temperature, oleogel samples

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containing 20% paraffin wax showed an unexpected increase in the solid fat content (SFC), as

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shown in Figure 3. One possible explanation is that when wax lamellae swell upon heating, more

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oil becomes trapped in between or adsorbed onto the surface of wax lamellae13. These surface-

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bound and confined oil molecules probably exchange at a lower frequency with the bulk oil

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phase and thus appear as “solid” in the pNMR measurement. A slight increment in SFC upon

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heating below the melting temperature was also observed in oleogel samples structured with 20%

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wax, where the wax phase contains a blend of 90% paraffin wax and 10% polyethylene wax,

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shown as Figure 3b. Increases in SFC upon heating seems to be specific to the paraffin wax

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oleogel, and no evidence was found in other oleogel systems, within the scope of our literature

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search.

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liquid oil

d

ξ

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Figure 4. Schematic diagram of cosmetic paraffin wax nanostructured oil.

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A schematic diagram of paraffin wax nanostructured oil can then be proposed (Figure 4).

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Results suggested that paraffin wax crystallized into the ß′ polymorphic form and arranged into

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lamellar structures, where oil can become trapped or bound between the lamellae. Even though

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only limited experimental evidence is available in the literature on confined/nanostructured oil, it

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may be present in other systems. One example is monoglyceride (MGs) oleogels. MGs have

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polymorphic and mesomorphic properties, and crystalize into lamellar structures that can

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immobilize both water and liquid oil17–21.Glycerol monostearate (GMS) crystallizes into a

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lamellar α phase with d001 at 50.7Å 22,23; while in a 90% oleogel structure, the d001 of the α phase

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increased to 52Å24. It is therefore plausible, based on results from the current work, that oil has

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been structured in between the GMS lamellae. However, whether nanostructured oil exists in

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MG-oil systems also remains unproven.

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To summarize, nanostructured confined oil was discovered in cosmetic paraffin wax –

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mineral oil systems in this work. Neat paraffin wax crystals and wax oleogel crystalized into the

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same polymorphic form, but oleogels had larger lamellar thickness and domain size. Increased

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lamellar thickness and domain size resulted from the swelling of wax lamellae upon

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nanostructuring of oil between them. These surface-bound/confined oil molecules had decreased

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mobility and displayed solid-like behavior at increasing temperatures. This experimental

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evidence for nanostructured oil between lamellar structures agrees with simulation studies. The

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generality of this type of oil binding at the nanoscale within lamellae and without loss in

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scattering coherence remains to be proven.

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145

References

146

(1)

Evans, R. J. Phys. Condens. Matter 1990, 2, 8989–9007.

147

(2)

Christenson, H. K.; Gruen, D. W. R.; Horn, R. G.; Israelachvili, J. N. J. Chem. Phys. 1987, 87, 1834–1841.

148 149

(3)

Maeda, N.; Christenson, H. K. Colloids Surfaces A Physicochem. Eng. Asp. 1999, 159, 135–148.

150 151

(4)

Porcheron, F.; Rousseau, B.; Fuchs, A. H. Mol. Phys. 2002, 100, 2109–2119.

152

(5)

Batman, R.; Gujrati, P. D. J. Chem. Phys. 2008, 127, 1–15.

153

(6)

Termonia, Y. Polymer (Guildf). 2011, 52, 5193–5196.

154

(7)

Razul, M. S. G.; MacDougall, C. J.; Hanna, C. B.; Marangoni, A. G.; Peyronel, F.; PappSzabo, E.; Pink, D. A. Food Funct. 2014, 5, 2501–2508.

155 156

(8)

MacDougall, C. J.; Razul, M. S.; Papp-Szabo, E.; Peyronel, F.; Hanna, C. B.; Marangoni, A. G.; Pink, D. A. Faraday Discuss. 2012, 158, 425.

157 158

(9)

Jones, R.; Kumar, S.; Ho, D.; Briber, R.; Russell, T. Nature 1999, 400, 146–149.

159

(10)

Müller, M. J. Chem. Phys. 2002, 116, 9930–9938.

160

(11)

Horn, R. G.; Israelachvili, J. N. Macromolecules 1988, 21, 2836–2841.

161

(12)

Liu, X. Y.; Bennema, P.; Meijer, L. A.; Couto, M. S. Chem. Phys. Lett. 1994, 220, 53–58.

162

(13)

Smith, P.; Lynden-Bell, R. M.; Smith, W. Mol. Phys. 2000, 98, 255–260.

163

(14)

Miyazaki, Y.; Marangoni, A. G. Mater. Res. Express 2014, 1, 1–12.

164

(15)

Timms, R. E. Aust. J. Dairy Technol. 1978, 33.

165

(16)

Humphrey, K. L.; Narine, S. S. In Fat Crystal Networks; Marangoni, A. G., Ed.; CRC Press: Boca Raton, Florida, 2004; pp. 83–114.

166 167

(17)

Larsson, K. Zeitschrift für Phys. Chemie Neue Folge 1967, 56, 173–198.


9


Page 10 of 15

168

(18)

Lutton, E. S. J. Am. Oil Chem. Soc. 1971, 48, 778–781.

169

(19)

Krog, N. In Food Emulsions; Friberg, S. E.; Larsson, K., Eds.; Marcel Dekker: New York, 1997; pp. 141–188.

170 171

(20)

Chen, C. H.; Terentjev, E. M. In Edible Oleogels: Structure and Health Implications; Marangoni, A. G.; Garti, N., Eds.; AOCS Press: Urbana, 2012.

172 173

(21)

Wang, F. C.; Marangoni, A. RSC Adv. 2014, 4, 50417–50425.

174

(22)

Lutton, E. S.; Jackson, F. L. J. Am. Oil Chem. Soc. 1948, 70, 2245–2249.

175

(23)

Lutton, E. S. J. Am. Oil Chem. Soc. 1950, 27, 276–281.

176

(24)

Chen, C. H.; Damme, I. Van; Terentjev, E. M. Soft Matter 2009, 6, 432–439.

177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202

Figure Legends

Figure 1. (a) XRD patterns of paraffin wax mixed with different amounts of oil, (b) lamellar thickness (d001) and crystal domain size (ξ) calculated form XRD data, (c) % increase in d001 and ξ of paraffin wax oleogel with different oil contents relative to neat paraffin wax crystals, and (d) correlation between % increase in d001 and % increase in ξ. Figure 2. (a) Melting profiles of paraffin wax structuring 0 to 80% (w/w) of oil, and (b) Hildebrand plot of paraffin wax – oil system. Figure 3. Amount of crystalline material determined as the solid fat content (SFC) of oil structured with (a) 20% (w/w) paraffin wax (n=4, error bars are all smaller than the symbols), and (b) 20% wt. wax that contains a blend of 90% paraffin wax and 10% straight chain polyethylene wax (n=2, error bars are all smaller than the symbols). Figure 4. Schematic diagram of cosmetic paraffin wax nanostructured oil.


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Figure 1. (a) XRD patterns of paraffin wax mixed with different oil content, (b) lamellar thickness (d001) and crystal domain size (ξ) calculated form XRD data, (c) % increase in d001 and ξ of paraffin wax oleogel with different oil content comparing to neat paraffin wax crystals, and (d) correlation between % increase in d001 and % increase in ξ. 100x62mm (600 x 600 DPI)



Figure 2. (a) Melting profiles of paraffin wax structuring 0 to 80% wt. of oil, and (b) Hildebrand plot of paraffin wax – oil system. 113x147mm (600 x 600 DPI)


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Figure 3. Amount of crystalline material determined as the solid fat content (SFC) of oil structured with (a) 20% wt. paraffin wax (n=4, error bars are all smaller than the symbols), and (b) 20% wt. wax that contains a blend of 90% paraffin wax and 10% straight chain polyethylene wax (n=2, error bars are all smaller than the symbols). 99x127mm (600 x 600 DPI)



Figure 4. Schematic diagram of cosmetic paraffin wax nanostructured oil. 36x27mm (300 x 300 DPI)


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Nanostructured Oil in Cosmetic Paraffin Waxes - ACS Publications

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