Phase behavior and rheological properties of enzymatically synthesized trehalose decanoate aqueous solutions.
J Colloid Interface Sci 2006;
294:187-93. [PMID:
16125719 DOI:
10.1016/j.jcis.2005.07.019]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Revised: 07/11/2005] [Accepted: 07/11/2005] [Indexed: 10/25/2022]
Abstract
Surface tension properties of an enzymatically synthesized equimolar mixture of trehalose mono- and didecanoate in aqueous solutions have been determined. At 20 degrees C a critical micellar concentration (CMC) of 50 micromol/l and a minimal surface tension of 28 mN/m have been obtained. Above the CMC, it has been shown that up to a concentration of 42 wt%, and in a 20-60 degrees C temperature range the sugar ester aqueous solutions do not form any crystalline structure, nor present any phase transition, and the trehalose decanoate molecules form an isotropic worm-like micellar phase. The rheological properties indicate however a more complicated picture in the same concentration and temperature ranges. In steady shear, the viscosity of the trehalose decanoate solutions do not exhibit any shear rate dependence from 1 to 100 s(-1) for concentrations up to 42 wt%. Below 0.8 wt%, the viscosity remains constant and close to that of water; then, between 0.8 and 23 wt%, the viscosity shows a quadratic increase with surfactant concentration. For higher concentrations, up to 42 wt%, no further significant increase in viscosity is observed. In oscillatory shear experiments, the solutions exhibit viscoelastic properties. The observed rheological behavior as a function of concentration and temperature may be due to a progressive evolution of the trehalose decanoate molecular associations: as the concentration increases, the system evolves towards an entangled and/or partially branched or cross-linked micellar network, and eventually a multiconnected network of cross-linked micelles.
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