Critical behavior of complex shear modulus in concentrated polymer solutions and gels

The critical anomaly in the complex shear modulus of an entangled polymer solution and a gel was studied. A system was constructed for measuring a complex shear modulus in the low-frequency range from 1 Hz to 500 Hz. Near the binodal line, the anomaly increases in both the real and the imaginary part of the complex shear modulus were observed in a concentrated solution of polymer. The elasticity is a result of strong entanglement. The critical anomaly in an entangled system may have a unique nature because of the elastic energy of the network. The temporal change of the complex shear modulus during phase separation can be measured using this system, since the time required for measuring the frequency spectrum is drastically shortened by applying the multifrequency excitation method