Rheology of the ultrasound-induced gelation in poloxamer aqueous solutions

The rheological behavior of the ultrasound-induced gelation of poloxamer aqueous solutions (Pluronic F-127, Sigma-Aldrich) is analyzed in this work. A new rheometric technique is proposed in which ultrasonic pulses are applied to the sample under shear flow. An ultrasonic transducer was adapted to the lower plate of a controlled-stress rheometer with a parallel-plate fixture (AR-1000 TA Instruments). Solutions were tested under linear oscillatory-shear flow at constant angular frequency in time sweeps with and without ultrasound. The mechanical response of the ultrasound-formed gels was evaluated under linear oscillatory and instantaneous stress relaxation tests. Results suggest that these solutions produce “weak gels” according to the Winter-Chambon criterion.