Rheological properties of thermo-responsive microemulsion-based gels formed by Pluronic F68

Xueyan Zhao* and Ruijie Xiao

Abstract

The thermo-responsive behavior of microemulsion-based gels (MBGs) formed by the triblock copolymer poly(ethylene oxide)-poly(propyleneoxide)-poly(ethylene oxide) (F68, PEO79PPO30PEO79) in microemulsion systems composed of isopropyl myristate (IPM)/Span20/Tween20/H2O were characterized by rheological measurements and fluorescence spectroscopy. The results of rheological measurements indicate that the viscosities of the gels increase and the gelation temperatures decrease with increasing F68 concentration. As a model drug, chloramphenicol has little effect on the viscosities and gelation temperatures of the MBG. Moreover, chloramphenicol is sustainably released from the MBG system. Fluorescence spectroscopy was used to study the micropolarity of the hydrogel (F68/H2O), microemulsion and MBG systems. The results show that the microstructures of microemulsion droplets are maintained in MBG after the addition of F68.