Rheological behaviours of the hexagonal and lamellar phases of glucopone (APG) surfactant

doi:10.1016/j.colsurfa.2005.10.004

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Volume 276, Issues 1–3, 15 March 2006, Pages 15-21

https://doi.org/10.1016/j.colsurfa.2005.10.004 Get rights and content

Abstract

The rheological behaviours of hexagonal and lamellar liquid crystalline phases of glucopone–water–hydrocarbon systems were investigated. Four different types of hydrocarbon namely heptane, octane, dodecane and tetradecane were considered. Small-angle X-ray scattering (SAXS) and optical polarizing microscopy were used for phase identification and structure characterization. The SAXS data was further analyzed in terms of lattice parameters and area per surfactant head group. The area head group of the hexagonal phases seemed not to depend on the alkane chain length. On the other hand, the area head group for the lamellar phases was found to increase as the alkane chain is lengthened. The frequency-dependent storage and loss modulus were found to exhibit characteristics of the hexagonal and lamellar phases in the linear viscoelastic regions. The elastic properties of hexagonal phases were also found to be unaffected when higher homologue of the alkane series was considered, while for lamellar phases the elastic properties were found to decrease. The effects of temperature on the rheological behaviours of hexagonal and lamellar phases were also investigated and their melting transition temperatures were found to be almost similar. Moreover, the melting transition temperatures determined by rheology differ only slight from that determined by microscopy. The rheological quantities were found to decrease when the temperature was increased. In general, the effects of different types of hydrocarbon in the rheological behaviours were found to be more profound in the lamellar than in the hexagonal phases.

Introduction

Considering the wide range of applications for surfactant-containing systems, detailed rheological characterizations becomes increasingly important, for example in the design of pumping, agitation and mixing operational units. Moreover, it also helps one to in establish theoretical understanding of the relationships between the viscoelastic properties and the microstructures. It has been known that such systems exhibit complex flow properties especially at high surfactant concentrations [1], [2].

The growing interest concerning sugar ester surfactants over petrochemically derived standard products is mainly due to their advantages with regard to performance and environmental compatibility [3], [4]. Moreover, sugar ester surfactants are mostly obtained from renewable raw materials such as fatty acids and sucrose [5], [6]. They are readily biodegradable in aqueous environments and in most situations found to be non-toxic and non-allergenic [3]. Hence, sugar surfactants are widely used in the fields of cosmetics [7], [8] and food additives [9] for a variety of functions that include emulsifying and foaming in various products such as bread, ice cream, margarine, and fat substitutes [10], [11], [12]. Studies on lyotropic behavior of amphiphilic sugar derivatives are still relatively limited [13], [14]. Interestingly, depending on the type of product being studied, an entire range of lyotropic mesophases ranging from hexagonal to reverse hexagonal via cubic fluid lamellar can be obtained. The lamellar phase is the most commonly prepared liquid crystal mesophase in concentrated surfactant systems. Considerable amount of work has been focused towards understanding the changes in the microstructure of the lamellar phase under shear. In particular, the effects of surfactant concentration on the rheology and microstructure of the lamellar phase have been recently reported [15]. The rheological response during processing is directly related to microstructural changes, which contributes to significant functional benefits. In contrast, the rheological behaviour of the hexagonal liquid crystals is less studied [16], [17]. They are known to be more viscous than the lamellar liquid crystals, with the viscosity decreasing as the shear rate is increased. They are also known to exhibit elastic properties [16].

In this work, the hexagonal and lamellar phases of the glucopone–water–hydrocarbon systems were considered. The phase behaviours of glucopone–water–hydrocarbone systems were investigated by Siddig et al. [18]. Optical microscopy and small-angle X-ray scattering (SAXS) were used for phase identification and structure characterization. SAXS experiments are useful in conveying information on the area per surfactant head group in the liquid crystalline phases. Rheological measurements were performed in order to study the viscoelastic properties of the liquid crystalline phases. The effects of different types of hydrocarbon and temperature on the rheological behaviours of hexagonal and lamellar phases were also investigated.

Section snippets

Material and samples preparation

Technical grade alkyl polyglucosides, APG (commercially known as glucopone 215 CSUP), octane and dodecane were purchased from Fluka. The APG represents a mixture of α- and β-glucosides [18] and is supplied as a 65 wt.% solution in water. The surfactant was used without any further purification. Heptane was purchased from Ajax chemicals, while tetradecane was purchased from Tokyo Kasei Kogyo Co. (TCI). The APG solution was prepared by weighing the surfactant into a glass tube and diluting it to

Small-angle X-ray scattering

The birefringence patterns of lyotropic mesophases of hexagonal and lamellar structures were observed first using an optical polarizing microscope. This was followed by SAXS measurement in order to confirm the formation of these phases. The characterization of liquid crystalline phases by X-ray diffraction is based on the long-range order in the liquid crystalline state which gives rise to Bragg reflections. The positions of peaks are characteristic of the different liquid crystalline phases.

Conclusions

The rheological behaviours of the hexagonal and lamellar liquid crystalline phases of glucopone–water–hydrocarbon systems have been investigated. The liquid crystalline phases were formed at high surfactant concentrations and were identified by means of microscopy and SAXS. The SAXS measurements showed that the area per head groups of hexagonal phases are almost unaffected, while the area per surfactant head groups for the lamellar phases were found to increase as the alkane chain length of

Acknowledgment

This work was supported by the Malaysian Ministry of Science, Technology and Environment, under research grant IRPA 09-02-02-0032-SR0004/04-04.

References (38)

M.A. Thevenin et al.
Int. J. Pharm.
(1996)
F.A. Husband et al.
Food Hydrocoll.
(1998)
N. Garti et al.
Colloids Surf. A: Physicochem. Eng. Asp.
(2000)
H. Kahl et al.
Colloids Surf. A: Physicochem. Eng. Asp.
(2001)
M.G. Berni et al.
Adv. Colloid Interface Sci.
(2002)
L. Coppola et al.
J. Colloid Interface Sci.
(2003)
M.A. Siddig et al.
Colloids Surf. A: Physicochem. Eng. Asp.
(2004)
F. Nilsson et al.
J. Colloid Interface Sci.
(1998)
M.G. Berni et al.
Adv. Colloid Interface Sci.
(2002)
S. Deguchi et al.
Colloids Surf. A: Physicochem. Eng. Asp.
(1999)

G. Marrucci

J. Non-Newtonian Fluid Mech.

(1996)

M. Gradzielski et al.

J. Colloid Interface Sci.

(1995)

J. Schulte et al.

Colloid Polym. Sci.

(1999)

H. Hoffmann et al.

I.J.A. Baker et al.

J. Surfact. Deterg.

(2000)

M. Ferrer et al.

Langmuir

(2002)

G. Fregapane et al.

J. Am. Chem. Soc.

(1994)

L. Cao et al.

Biocatal. Biotransform.

(1998)

N.B. Desai

Cosmet. Toiletries

(1995)

Cited by (40)

Effect of glycerol incorporation on the liquid crystal structure of sucrose fatty acid ester in aqueous solution
2024, Colloids and Surfaces A: Physicochemical and Engineering Aspects
A series of homogeneous samples with high sugar-surfactant content (sucrose fatty acid ester/water and sucrose fatty acid ester/glycerol/water systems) were prepared with well-controlled processes and investigated by DSC, polarized microscopy, X-ray scattering and rheology. Meanwhile the accuracy of the preparation process is confirmed gas chromatography. The polarized microscopy indicates that the ordering degree of the network structure composed of the liquid crystals may be reduced by the glycerol addition. The results of DSC revealed that 50% glycerol solution could significantly inhibit the crystallization of sucrose fatty acid ester and resulted in a significant widening of the temperature interval for the transformation of the liquid crystal phase into the gel phase. In order to further evaluate the effect of glycerol molecules versus water molecules on the liquid crystal structure of sucrose fatty acid ester, we comparatively analyzed the X-ray scattering data from two perspectives: the mass fraction and molar fraction. It was found that 50% glycerol solution could inhibit the crystallization of sucrose fatty acid ester through changing the water-head group interaction of surfactant, facilitates the integration of sucrose fatty acid ester with different alkyl chain length and may reduce the regularity of liquid crystal, both from the perspective of surfactant mass and molar fraction. Furthermore, the addition of 50% glycerol (w/w) does not significantly impede the liquid crystal formation of sucrose fatty acid ester in aqueous solution. However, from the perspective of surfactant mass fraction, glycerol incorporation could reduce the effective cross-sectional areas of the hydrophilic part of sucrose fatty acid ester in aqueous solution and induce the phase transition of hexagonal liquid crystals to aggregates with less positive curvature, while an opposite tendency could be obtained from the perspective of surfactant molar fraction. The conclusions are also confirmed by subsequent rheological test. Moreover, the results of rheological measurements reveals that the interactions among cylindrical units of the hexagonal liquid crystalline phase become weaker and the surfactant molecules aggregate more loosely in the cylindrical unit with the glycerol incorporation. Moreover, the above-mentioned influence of glycerol on the liquid crystal structure of sucrose fatty acid ester in aqueous solution would be similar but more prominent from the perspective of the molar fraction.
Phase diagrams and property of colloidal systems prepared with an alkyl polyglucoside surfactant and the essential oil of Melaleuca alternifolia (tea tree)
2023, Journal of the Taiwan Institute of Chemical Engineers
The purpose of this study was to develop the colloidal formulation, based on microemulsions and hydrogels, of Melaleuca alternifolia oil (aka tea tree oil, TTO) using a sustainable and biocompatible alkyl polyglucoside (APG) surfactant, Glucopon 600 CSUP (G600), commonly formulated for personal-care and home-care products.
The pseudo-ternary phase diagram of TTO-mixed surfactant-water was established with the water titration method at 25 °C. The mixed surfactants were composed of G600 and propylene glycol (PPG) as a co-surfactant at G600/PPG = 1/1, 2/1 and 3/1 (m/m). Colloid samples of one phase were further characterized with rheological measurements and dynamic light scattering (DLS) at 25 °C.
The samples containing TTO/mixed surfactant = 1/9 (m/m) and water show single phase only. With increasing water contents, the aforesaid system changed from Newtonian to pseudo-plastic, reflecting the transition from micellar solution / microemulsion to hydrogel. Especially, the gel-like behavior was confirmed with the dynamic oscillatory measurements, in which storage moduli were always larger than loss moduli at any time and any frequency under a constant strain of 0.5 %. Microemulsions made of 1 wt% tea tree oil and 9 wt% mixed surfactants were stable for > 1 month as monitored by aggregate size by DLS.
Improvement in lubricating properties of TritonX-100/n-C<inf>10</inf>H<inf>21</inf>OH/H<inf>2</inf>O lamellar liquid crystals with the amphiphilic ionic liquid 1-alkyl-3-methylimidazolium hexafluorophosphate
2018, Journal of Colloid and Interface Science
Citation Excerpt :
In addition, the CnmimPF6 with longer chain lengths tend to increase the bilayer thickness d0, which results in the reduced interaction of the amphiphilic molecular and the weakened rigid structure of LLCs. These results agree with the theory proposed by Siddig [42] that the area per surfactant head groups for the lamellar phases were reduced as the alkane chain length of hydrocarbon increased. The effects of added CnmimPF6 on the tribological properties of the LLCs were investigated.
The applications of ionic liquids (ILs)/lamellar liquid crystals (LLCs) have great potential in nanotribology because they could be used where conventional oils could not work. To clarify the lubricating mechanism, herein, ILs/LLCs lubricants were prepared by addition of amphiphilic 1-alkyl-3-methylimidazolium hexafluorophosphate (C_nmimPF₆, n = 8, 12) into TritonX-100/n-C₁₀H₂₁OH/H₂O LLCs with different concentration. The influence of alkyl chain lengths of ILs on the microstructures and the tribological properties of LLCs were investigated. The phase structure parameters and the tribological properties of the LLCs in the presence of C_nmimPF₆ were analyzed via freeze-fracture transmission electron microscopy (FF-TEM), the small-angle X-ray scattering (SAXS) technique, oscillating reciprocating friction and wear tester. Compared with the LLCs without C_nmimPF₆, 4.5 wt% C_nmimPF₆ /LLCs can reduce the friction and wear of sliding pairs. The better lubricating property and antiwear capability of the C_nmimPF₆/LLCs may be attributed to the increasing of the interlayer thickness d and the decreasing of the bilayer thickness d₀ in microstructures. This work provides a better understanding of the relationship between the microstructures and friction wear performances of ILs/LLCs.
The alkyl polyglucoside/fatty alcohol ratio effect on the formation of liquid crystal phases in binary systems
2018, Journal of Molecular Liquids
Citation Excerpt :
This information helps to clarify that the microscopic observations under the polarized light do not belong to lamellar phase; APG < FA: storage modulus is parallel to loss modulus, corresponding to lamellar phase behaviour [41–43], thus confirming the microscopic observations (Fig. 5b); APG = FA: these products showed a more lamellar like response to the solicitation, with parallel curves and weak frequency dependence of both G′ and G″, but with lower values of both moduli (Fig. 5c).
The present research focuses on the alkyl polyglucoside, a non-ionic surfactant, in combination with a fatty alcohol of the same chain length used as a co-surfactant. A series of solutions were prepared, with varying both APG/FA ratio and its concentration in water. Different structures were then obtained, depending on these two parameters: aqueous micellar solutions, normal hexagonal liquid crystalline phase, α-gel phase, as well as the mixture of normal hexagonal/α-gel phases. A specific term “auto-emulsion” was introduced to describe the pseudo emulsions formed by the APG ≤ FA containing solutions because of the fatty alcohol, which dispersion in water was similar to an emulsion representation. The presence of the liquid crystals was revealed by optical microscopy under the polarized light, as different anisotropic conformations corresponding to the lamellar phase, the hexagonal phase and the coexistence of the lamellar and hexagonal phases, mainly for the most concentrated samples, were observed. These structures were characterized at the molecular level through the wide-angle X-ray diffraction technique and their macroscopic behaviour was investigated by rheology tests. Two main observations were then made: the variation of the surfactant concentration in solution promotes the transition between micellar region towards the liquid crystalline formation zone, while the APG/FA ratio impacts the formation of hexagonal phases (APG > FA) or of lamellar ones (APG < FA).
Influence of the emollient structure on the properties of cosmetic emulsion containing lamellar liquid crystals
2018, Colloids and Surfaces A: Physicochemical and Engineering Aspects
Citation Excerpt :
For this purpose, complementary rheological tests and X rays analysis were carried out. The results of the frequency test are presented as G’ and G” moduli as a function of frequency: for the emulsions containing A group Fig. 7a and B group oils Fig. 7b. For the seven emulsions storage modulus is parallel to loss modulus, corresponding to lamellar phase behavior [35–37]. Meanwhile, one can observe the differences in G” modulus behavior between two groups of oils which implies changes in tanδ and, consequently, in viscoelastic properties of the samples as already shown.
In the present study the effect of cosmetic emollients (oils and esters) varying from their chemical structure on the lamellar liquid crystals organization has been investigated. The cetearyl alcohol/cetearyl glucoside emulsifier, known for its ability to form lamellar phases was used at a level of 10% in emulsions. At this high concentration a strong lamellar network is formed. Also, each of the seven selected emollients was incorporated at level of 20%, as for a classical cosmetic emulsion. These quantities were necessary in order to assure the presence of lamellar phases in all the samples and to amplify the impact of the emollient on the structural organization of the surfactant. Additionally, a control sample was formulated, containing only emulsifier and water. Emollients were divided as a function of their chemical structure in group A (without heteroatom) and B (with heteroatom). They were first described as a function of the interfacial tension against water, in order to classify them according to their hydrophobicity.
The presence of the lamellar phases in all samples was confirmed by means of optical microscopy under polarized light, and then the differences between emulsions physical properties were evidenced by static light scattering and rheological measurements. It was shown that use of A group emollients induces larger droplets size and, respectively, more elastic behavior to the emulsions. This phenomenon is related to the lamellar organization, which is dominated by α-gel for A group oils and by lamellar liquid crystals combined to α-gel for B group emollients, as showed through wide angle X-ray diffraction technique. Moreover, the influence of such structures on usage properties of emulsions was characterized via thermal analyses and spreadability tests.
Phase equilibria of mixtures of surfactants and viscoelastic properties of the liquid crystal phases
2016, Fluid Phase Equilibria
Citation Excerpt :
The H1 phase for C12E4 contents higher than 15% in the mixture coexist with lamellar phase. Similar values of the relaxation times were obtained for hexagonal phase of glucopones surfactants [31]. The elastic properties ware also associated to the area per surfactant molecule.
Mixtures of surfactants are widely used in many industrial and pharmaceutical products. Whereas diluted mixtures of surfactants have been studied in deep, much lesser studies at high surfactant concentrations have been made. A comparative study among the different systems of tetraoxyethylene dodecyl ether (C₁₂E₄) with different nonionic and anionic surfactants has been carried out. Four phase diagrams of C₁₂E₄/C₁₂E₁₀/water, C₁₂E₄/S40P/water, C₁₂E₄/SDS/water and C₁₂E₁₀/SDS/water systems at 30 °C are reported. In all of them, mixed micelles in water and reverse micelles have been found. Lamellar and hexagonal are the liquid crystals which appear in these ternary systems. Liquid crystals have been characterized by polarized light microscopy and rheology. Viscoelastic properties of the liquid crystals have been determined. Lamellar phase behaves like a gel with both mechanical moduli (G′ and G″) independent on frequency. The elastic properties of the lamellar phase are strongly dependent of the presence of ionic charges. Lamellar liquid crystals for the mixture with the anionic surfactant (SDS) have the higher elastic modulus. For hexagonal phase, elastic and viscous moduli increase with increasing frequency but with different slopes. Its elastic properties are strongly dependent of critical packing parameter of surfactants. Hexagonal liquid crystals for the mixtures with C₁₂E₄ (surfactant with the smaller area of the head group) show the more important elastic properties.

View all citing articles on Scopus

View full text

Rheological behaviours of the hexagonal and lamellar phases of glucopone (APG) surfactant

Abstract

Introduction

Section snippets

Material and samples preparation

Small-angle X-ray scattering

Conclusions

Acknowledgment

Int. J. Pharm.

Food Hydrocoll.

Colloids Surf. A: Physicochem. Eng. Asp.

Colloids Surf. A: Physicochem. Eng. Asp.

Adv. Colloid Interface Sci.

J. Colloid Interface Sci.

Colloids Surf. A: Physicochem. Eng. Asp.

J. Colloid Interface Sci.

Adv. Colloid Interface Sci.

Colloids Surf. A: Physicochem. Eng. Asp.

J. Non-Newtonian Fluid Mech.

J. Colloid Interface Sci.

Colloid Polym. Sci.

J. Surfact. Deterg.

Langmuir

J. Am. Chem. Soc.

Biocatal. Biotransform.

Cosmet. Toiletries