Rheology of mesogels

(Received 24 August 1992, raccepted 7 September 1992)

Abstract
The effect of triblock copolymers (polyoxyethylene-polyisoprene-polyoxyethylene) on the interaction potential and network formation of nanodroplets in w/o microemulsions, i.e. on the formation of "mesogels", has been studied by flow- and oscillatory shear measurements. Frequency dependent storage and loss moduli, the zero shear viscosity and the terminal relaxation times were determined which agree well with predictions from scaling laws for homopolymer solutions ; lifetimes of network crosslinks were determined from the transition of Newtonian to viscoelastic behaviour that agree with the characteristic time constant which correspond to the crossover from restricted to free diffusion of the copolymer. The activation energy of viscous flow at large copolymer concentrations shows a logarithmic concentration dependence from which a power law dependence of the viscosity against copolymer concentration can be derived if an Arrhenius relation for the temperature dependent viscosity is assumed.