I. Alig et al., Order-to-disorder transition in a diblock copolymer studied at ultrasonic frequencies with a shear wave reflection technique, EUROPH LETT, 52(3), 2000, pp. 291-296
The order-to-disorder transition (ODT) has been studied in a poly(styrene-b
-isoprene) diblock copolymer with conventional rheology and an ultrasonic s
hear wave reflection technique. Despite the operational frequency in the la
tter experiment (f = 5 MHz) being much higher than the critical frequency o
mega (c), the storage modulus exhibits a discontinuous increase at the same
temperature at which in conventional rheology a discontinuous decrease is
obtained. This results from a change in the mixing law at the ODT. The meth
od constitutes a nondestructive probe of the viscoelastic properties of "so
ft" materials in the vicinity of phase transitions.