Nonionic Amphiphilic Bilayer Structures under Shear

Le, T. D.; Olsson, Ulf; Mortensen, K.; Zipfel, J.; Richtering, Walter

doi:10.1021/la001227a

Cited by 82 publications

(119 citation statements)

References 36 publications

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“…For the present composition, d=6 nm [8,25,26]. With these values for c and d and the temperature T=298 K, we obtain b/c=14.9 Pa s 1/2 , which is approximately twice the measured value.…”

Section: Polarized Light Microscopysupporting

confidence: 54%

“…The MLVs at higher surfactant concentrations are polyhedral. They fill space with a total volume fraction which is essentially unity [8,34] and N/V is approximately proportional to R )3 .…”

Section: Introductionmentioning

confidence: 99%

“…In fact, many different shear effects have been reported: transformation from lamellar phases to Multi-lamellar vesicles, MLVs (or ''onions''), in different amphiphilic systems and followed by different techniques [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]; formation of MLVs in presence of submicron-size particles (''stuffed onions'') [21]; changes in lamellar orientation [17,22,23]; formation of intermediates with cylindrical structure between a lamellar and MLV phases [24][25][26]; reduction in lamellar spacing [27]; transitions from MLVs to unilamellar vesicles [28] and ''layering'' effects on onions [8,29]. As a practical application, these MLVs can be used, for instance, to encapsulate chemicals leading to a new kind of controlled micro-reactor [30] or as carriers for oligonucleotide delivery [31].…”

mentioning

confidence: 99%

“…The MLVs at higher surfactant concentrations are polyhedral. They fill space with a total volume fraction which is essentially unity [8,34] and N/V is approximately proportional to R )3 . Abstract We have investigated the reversibility in the shear-induced multi-lamellar vesicle (MLV) size during stepwise cycling of the shear rate by employing common rheometry, polarized light microscopy and rheo-optic techniques.…”

mentioning

confidence: 99%

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Reversible size of shear-induced multi-lamellar vesicles

et al. 2005

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IntroductionThe behavior of lamellar phases under shear is a subject that has been receiving a lot of attention in the recent years [1][2][3][4]. In fact, many different shear effects have been reported: transformation from lamellar phases to Multi-lamellar vesicles, MLVs (or ''onions''), in different amphiphilic systems and followed by different techniques [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]; formation of MLVs in presence of submicron-size particles (''stuffed onions'') [21]; changes in lamellar orientation [17,22,23]; formation of intermediates with cylindrical structure between a lamellar and MLV phases [24][25][26]; reduction in lamellar spacing [27]; transitions from MLVs to unilamellar vesicles [28] and ''layering'' effects on onions [8,29]. As a practical application, these MLVs can be used, for instance, to encapsulate chemicals leading to a new kind of controlled micro-reactor [30] or as carriers for oligonucleotide delivery [31].The size distribution of shear-induced multi-lamellar surfactant vesicles depends on the applied shear rate. In general, the MLV systems are shear thinning and the average MLV radius, R, decreases as the shear rate increases [5,26,32]. For higher surfactant concentrations, the inter-bilayer spacing is independent of the MLV size [33]. Hence, a decrease in the MLV size is accompanied by an increase in the MLV number density, N/V, where N is the number of vesicles and V the total volume. The MLVs at higher surfactant concentrations are polyhedral. They fill space with a total volume fraction which is essentially unity [8,34] and N/V is approximately proportional to R )3 . Abstract We have investigated the reversibility in the shear-induced multi-lamellar vesicle (MLV) size during stepwise cycling of the shear rate by employing common rheometry, polarized light microscopy and rheo-optic techniques. We thus address the question whether there is a true MLV steady state, irrespective of history. The system studied, was the nonionic surfactant triethylene glycol decyl ether (C 10 E 3 ) with a concentration of 40 wt.% in D 2 O and a constant temperature of 25°C. It was found that the MLV size varies reversibly with varying shear rate, and hence there exists a true steady state in the presence of shear flow. The experimental observations of reversibility are however restricted to higher shear rates. Because the transformation of the size results from the shear strain, the process is very slow at lower shear rates, where the steady state cannot be reached within a reasonable experimental time.

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“…For the present composition, d=6 nm [8,25,26]. With these values for c and d and the temperature T=298 K, we obtain b/c=14.9 Pa s 1/2 , which is approximately twice the measured value.…”

Section: Polarized Light Microscopysupporting

confidence: 54%

“…The MLVs at higher surfactant concentrations are polyhedral. They fill space with a total volume fraction which is essentially unity [8,34] and N/V is approximately proportional to R )3 .…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Reversible size of shear-induced multi-lamellar vesicles

et al. 2005

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“…As has already been shown in the C 10 E 3 system (Le et al, 2001;Oliviero et al, 2003), the fraction of onions under shear flow strongly depends on temperature. In our previous SAXS study on the C 16 E 7 system at rest, we have shown that bilayers in the lamellar phase have water-filled defects below about 341 K and that the fraction of the defects increases with decreasing temperature (Minewaki et al, 2001).…”

Section: Figuresupporting

confidence: 55%

Shear-induced structural transition in the lamellar phase of the C₁₆E₇/D₂O system. Time evolution of small-angle neutron scattering at a constant shear rate

et al. 2007

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The time evolution of small-angle neutron scattering is measured for the lamellar phase of a nonionic surfactant C 16 H 33 (OC 2 H 4 ) 7 OH (C 16 E 7 ) in D 2 O at 48 wt% at 343 K under shear flow. At the shear rates of 0.3, 1 and 3 s À1 , a new diffraction peak appears at higher q [where q = (4 / )sin , and and 2 are the wavelength of the neutron beam and the scattering angle, respectively] about 1-2 h after applying shear flow and coexists with the initial diffraction peak. The coexistence of two peaks continues even after 5 h at 0.3 s À1 whereas at 1 and 3 s À1 the peak at lower q disappears after about 3 h. These results indicate that the repeat distance decreases discontinuously and so suggest some sort of transition. A plot of the repeat distance after 5 h versus shear rate shows a minimum at 1 s À1 , which is in good agreement with our previous results obtained by increasing the shear rate stepwise.

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