Abstract
The phase behavior and rheological properties of a lyotropic liquid crystal formed in the lecithin/AEO20/IPM/H2O system were investigated by means of phase diagram, polarized optical microscopy and rheology techniques at 37°C. After adding polyoxyethylene-20-oleyl ether (AEO20) and isopropyl myristate (IPM) to lecithin solutions, an isotropic liquid phase and an anisotropic liquid crystal phase were found. By analyzing the shear viscosity (ηγ=0.1) and yield stress (σ0), with increase in water content, the ηγ=0.1 and σ0 increase firstly and then decrease; with increasing IPM content, a decrease in the ηγ=0.1 and σ0 is observed. Notably, at the relatively higher water content area, the water content has little effect on the ηγ=0.1 and critical stress. When the lecithin/AEO20 mass ratio is 1:2, the liquid crystal phase displays a stronger shear resistance and more stable network structure.
Kurzfassung
Das Phasenverhalten und die rheologischen Eigenschaften des lyotropen Flüssigkristalls, der in dem System Lecithin/AEO20/IPM/H2O erzeugt wurde, wurden mittels des Phasendiagramms, der Polarisationslichtmikroskopie und rheologischer Messungen bei 37°C untersucht. Nach Zugabe von Polyoxyethylen-20-oleylether (AEO20) und Isopropylmyristat (IPM) zu den Lecithinlösungen wurden eine isotrope Flüssigphase und eine anisotrope Flüssigkristallphase gefunden. Durch Analyse der Scherviskosität (ηγ=0.1) und der Fließspannung (σ0) bei steigendem Wasseranteil nahmen ηγ=0.1 und σ0 zunächst zu und fielen dann ab; bei steigendem IPM-Gehalt wurde ein Abfall von ηγ=0.1 und σ0 beobachtet. Speziell in dem Bereich mit relativ höheren Wassergehalten hatte der Wassergehalt kaum Einfluss auf die Scherviskosität (ηγ=0.1) und die Fließspannung (σ0). Wenn das Massenverhältnis von Lecithin zu AEO20 1:2 betrug, besaß die Flüssigkristallphase einen höheren Scherwiderstand und eine stabilere Netzstruktur.
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