Shear-induced phase transitions in sucrose ester surfactant (original) (raw)
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Colloid and Polymer Science, 2017
A sponge phase (L 3 phase) was observed in aqueous solution of a nonionic surfactant polyethylene glycol ether of tridecyl alcohol with the average 3 of ethylene oxide (CH 3 (CH 2) 12 (OCH 2 CH 2) 3 OH, abbreviated as Trideceth-3) with tetradecyldimethylamino oxide (CH 3 CH 2 ð Þ 13 N ↑ O CH 3 ð Þ 2 , abbreviated as C 14 DMAO). The L 3 phase can be transferred to planar lamellar phase after the bilayer was protonated by the formic acid formed through the hydrolysis of methylformate. The addition of surface charge into the nonionic L 3 phase through electrostatic repulsion on the ionic head groups will suppress the Helfrich undulation and induce the transition to planar lamellar phase. The planar lamellar phase can be transformed into multilamellar vesicles under shear. Rheological properties show that both of the storage modulus and the loss modulus of the lamellar phase were increased with the increment of surface charge density. The phase transition from L 3 phase to vesicles was characterized by rheological measurements, 2 H NMR spectra, and transmission electron microscope (TEM) observations. To our best knowledge, this is the first example of a controlled phase transition in nonionic surfactant mixtures through protonation and shear forces. The procedure provides a direction on how to achieve phase transition in surfactant solution by changing the conditions and an application of phase transition of controlled materials.
Multi-lamellar vesicle formation in a long-chain nonionic surfactant: C16E4/D2O system
Journal of Colloid and Interface Science, 2011
The temperature dependent rheological and structural behavior of a long-chain C 16 E 4 (tetraethylene glycol monohexadecyl ether) surfactant in D 2 O has been studied within the regime of low shear range. In the absence of shear flow, the system forms a lamellar liquid crystalline phase at relatively high temperatures. The present paper reports on the shear-induced multi-lamellar vesicle (MLV) formation in C 16 E 4 /D 2 O at 40 wt.% of surfactant in the temperature range of 40-55°C. The transition from planar lamellar structure to multi-lamellar vesicles has been investigated by time-resolved experiments combining rheology and nuclear magnetic resonance (rheo-NMR), rheo small-angle neutron scattering (rheo-SANS) and rheometry. The typical transient viscosity behavior of MLV formation has been discovered at low shear rate value of 0.5 s À1 .
Rheological behaviour of a lamellar liquid crystalline surfactant–water system
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1998
The rheological behaviour of a lamellar liquid crystalline surfactant-water system was investigated using a Haake RS-100 viscometer. The repeat distance of lamellae as a function of surfactant concentration and temperature was measured by small-angle X-ray scattering. The rheological characteristics were measured at different temperatures with systems containing surfactant in different concentrations. The frequency-dependent storage and loss modulus were found to be characteristic to the lamellar phase in the linear viscoelastic region. The results are analysed on the basis of Jones-McLeish slip-plane theory. Trends of the fitted constants are discussed based on the general knowledge on the interactions in dispersions stabilized by non-ionic surfactants, and the structure of lamellar liquid crystalline samples. Time-dependent compliance was also measured. The instantaneous elasticity measured in the creep tests was compared with that predicted from oscillatory tests. Burger's model was used to describe the time-dependent compliance. Viscosity measurements in the non-linear region were also done. A modified Carreau equation is used to describe the viscosity versus shear rate curves. The changes in sample under shear is described briefly.
Study of thermosensitive gel-forming properties of sucrose stearates
Sucrose esters (SEs) are biodegradable surfactants that can be manufactured in various hydrophilic-lipophilic balances (HLB) through the use of different fatty acids. They are used in food and in industries, such as the cosmetics, detergents and pharmaceutical industries. In aqueous media they can form gels, which can affect various industrial processes. The pharmaceutical industry is currently showing an increasing preference for biomaterials and environmentally sensitive gels, and in particular thermo-sensitive gels. By virtue of the nontoxic, biodegradable and gel-forming properties of SEs, they are promising materials with which to form thermo-sensitive delivery systems. In this study, the gelling properties of some sucrose stearates were investigated by rheological measurements, and compared with each other. The effects of the release of gel-forming SEs on a model drug (paracetamol) were evaluated through in vitro drug release studies. The rheological results indicated that the sucrose stearates with lower HLB values have higher gel strengths than those of the more hydrophilic sucrose stearates. The gelling of the SEs is concentration-and temperature-dependent, and this gelling behaviour is responsible for the great effect of sucrose stearates on drug release.
Rheology, Optical Microscopy, and Electron Microscopy of Cationic Surfactant Gels
Journal of Colloid and Interface Science, 1996
Upon increasing the surfactant concentration, however, a A cationic surfactant mixture is studied in aqueous solution variety of phase structures may appear. Initially, the system by rheological and imaging techniques. We find that the system generally becomes significantly more viscous and then, at becomes gel-like above a threshold surfactant concentration, as sufficiently high concentrations, it may become viscoelastic, evidenced by the appearance of an apparent yield stress and a behavior indicative of network formation. Under small viscosity which is highly non-Newtonian. Hysteresis is observed stresses these concentrated lyotropic systems are primarily in the shear stress vs shear rate measurements: the formation of elastic, i.e., they exhibit an equilibrium modulus, although shear-induced microstructures at high shear rates may cause shear they flow above a limiting yield stress value (10). The rheothickening. Electron micrographs indicate three distinct structures logical and mechanical properties of surfactant gels are diin the sample: lamellae, large onion-like globules, and small nodules. These structures are discussed in the context of the rheologi-rectly linked to the structure of the network which is formed cal data. The density of the globular structures in sheared samples by the self associating molecules and to the various interacis observed to be larger than in unsheared samples. ᭧ 1996 Academic tions between the micellar aggregates (2, 3). This gel-like Press, Inc. behavior may be commercially important since concentrated Key Words: surfactant gels; rheology; electron microscopy; comsurfactant solutions are frequently used in paints, cosmetics, plex fluids; micelles. and the food industry. In the detergent industry, on the other hand, surfactants are used for their surface active properties, and viscous concentrated formulations are often undesirable 261
Flow behavior of sucrose stearate/water systems
Journal of the American Oil Chemists Society, 1992
The Rim of this work was to carry out a rheologicai study of aqueous systems containing a noniouic surfaetant derived from sugar. The compositions studied ranged from the micellar region up to the occurrence of fully developed liquid crystals. This study was tailed out at 50°C.
Lamellar Gels and Spontaneous Vesicles in Catanionic Surfactant Mixtures
Langmuir, 2006
Caillé analysis of the small-angle X-ray line shape of the lamellar phase of 7:3 wt/wt cetyltrimethylammonium tosylate (CTAT)/sodium dodecylbenzene sulfonate (SDBS) bilayers shows that the bending elastic constant is κ) (0.62 (0.09)k B T. From this and previous results, the Gaussian curvature constant is κ j) (-0.9 (0.2)k B T. For 13:7 wt/wt CTAT/SDBS bilayers, the measured bending elasticity decreases with increasing water dilution, in good agreement with predictions based on renormalization theory, giving κ o) 0.28k B T. These results show that surfactant mixing is sufficient to make κ ≈ k B T, which promotes strong, Helfrich-type repulsion between bilayers that can dominate the van der Waals attraction. These are necessary conditions for spontaneous vesicles to be equilibrium structures. The measurements of the bending elasticity are confirmed by the transition of the lamellar phase of CTAT/SDBS from a turbid, viscoelastic gel to a translucent fluid as the water fraction is decreased below 40 wt %. Freeze-fracture electron microscopy shows that the gel is characterized by spherulite defects made possible by spontaneous bilayer curvature and low bending elasticity. This lamellar gel phase is common to a number of catanionic surfactant mixtures, suggesting that low bending elasticity and spontaneous curvature are typical of these mixtures that form spontaneous vesicles.