Phase behavior and rheological properties of enzymatically synthesized trehalose decanoate aqueous solutions.
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.
Choplin
L
L
Centre de Génie Chimique des Milieux Rhéologiquement Complexes, INPL-ENSIC, 1 rue Grandville, BP 20451, 54001 Nancy Cedex, France. lionel.choplin@ensic.inpl-nancy.fr
Sadtler
V
V
Marchal
P
P
Sfayhi
D
D
Ghoul
M
M
Engasser
J-M
JM
D003432:Cross-Linking Reagents / Q000737:chemistry; D003651:Decanoates / Q000138:chemical synthesis*; D008823:Micelles; D015394:Molecular Structure; D044367:Phase Transition; D012212:Rheology; D033081:Shear Strength; D012996:Solutions / Q000737:chemistry; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D014199:Trehalose / Q000378:metabolism*; D014783:Viscosity; D014867:Water / Q000737:chemistry*
D003432:Cross-Linking Reagents; D003651:Decanoates; D008823:Micelles; D012996:Solutions; D013501:Surface-Active Agents; D014867:Water; D014199:Trehalose