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Luigi Coppola, Domenico Gabriele, Isabella Nicotera, Cesare Oliviero
MRI Experiments as a Tool to Study Asymptotic-Shear Flow Behaviour of a Worm-Like Reverse Micellar Phase

Appl. Rheol. 16:4 (2006) 190-197

This paper deals with a Magnetic Resonance micro-Imaging (MRI) analysis of asymptotic kinematics which is a condition adopted in some rheological characterisations. Asymptotic kinematics (for example the slow shearing ) aim is to evaluate material properties at ''equilibrium'', avoiding structural changes induced by external stimuli. Measured material functions in these mechanical conditions deal with the structure/morphology of materials and can be used to investigate the structure as a function of the state variables only, as temperature, pressure and composition. In this paper MRI experiments were performed to study some shear flow behaviours of surfactant wormy micelles made by lecithin/water and diluted in cyclohexane (reverse micellar phase L2). MRI was used as a non-invasive tool in order to follow the structural responses both during slow shearing and when the sample is stirred outside the linear behaviour range. Relations can be found between the typical NMR parameters, strictly related to the microstructure, and the rheological macroscopic parameters as zero-shear viscosity.

Cite this publication as follows:
Coppola L, Gabriele D, Nicotera I, Oliviero C: MRI Experiments as a Tool to Study Asymptotic-Shear Flow Behaviour of a Worm-Like Reverse Micellar Phase, Appl. Rheol. 16 (2006) 190.

Luigi Coppola, Isabella Nicotera, Cesare Oliviero
Dynamic Rheological Analysis of MLVs and Lamellar Phases in the System C_12 E_4/D_2O

Appl. Rheol. 15:4 (2005) 230-237

The mechanical properties of the lamellar phase, La, of the system C_12 E_4/D_2O were studied along an isoplethal path (30 wt% C_12 E_4) in the temperature range 10 - 60 C. A dynamic analysis was determined by small strain oscillatory rheometry. The multilamellar vesicles (MLVs) (onions) were transformed by shearing the lamellar phase. The micellar phase was investigated by steady and dynamic rheological experiments. The micellar aggregate size increases slightly upon heating and the transition from micelles to lamellae appears to be a first order transition. The mechanical spectra of the lamellar phase show a strong dependence of the moduli on the frequency. This is typical of defective lamellar phases. They are different from MLVs mechanical spectra. The MLVs viscous and storage moduli are almost independent from the frequency and they exhibit the characteristics of a strong gel. The temperature of formation of the MLVs phase influences the mechanical properties of the MLVs. Three different packing states of the MLVs phase were observed in the temperature range 25 - 55 C.

Cite this publication as follows:
Coppola L, Nicotera I, Oliviero C: Dynamic Rheological Analysis of MLVs and Lamellar Phases in the System C_12 E_4/D_2O, Appl. Rheol. 15 (2005) 230.

Luigi Coppola, Domenico Gabriele, Isabella Nicotera, Cesare Oliviero
Rheological Properties of the Reverse Mesophases of the Pluronic L64/P-Xylene/Water System

Appl. Rheol. 14:6 (2004) 315-323

The behaviour of reverse micellar solution and reverse hexagonal and lamellar liquid crystal phases in pluronic L64/water/p-xylene ternary system was investigated by rheological techniques. Samples with an increasing water content along the amphiphilic copolymer-lean side of the ternary phase diagram were analysed at different temperatures and a different behaviour was evidenced by both dynamic and steady tests for each considered phase, depending on the morphology of structure (micellar, lamellar, hexagonal phases). It was observed that the reverse micelles size increases with increasing water concentration and decreases with increasing temperature, without any phase transition. On the contrary the normal micelles become anisometric on temperature, showing a transition to a liquid crystalline phase. The observed mechanical spectra of the liquid crystalline phases are typical of hexagonal and lamellar phases according to the literature. A phase transition with temperature was found for both liquid crystalline phase (lamellar and hexagonal) by rheological tests and was confirmed by ocular inspection.

Cite this publication as follows:
Coppola L, Gabriele D, Nicotera I, Oliviero C: Rheological Properties of the Reverse Mesophases of the Pluronic L64/P-Xylene/Water System, Appl. Rheol. 14 (2004) 315.


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