AbstractUltrasonic absorption measurements were carried out on solutions of polybenzyl‐L‐aspartate (PBLA) in chloroform–dichloroacetic acid (DCA) and in 1,2‐dichloroethane (DCE)–DCA, in the range 3.9–155 MHZ. The helix–coil transition of PBLA produces an increase of absorption which is larger in CHCl3–DCA than in DCE–DCA solutions. The influence of the solvent on the excess ultrasonic absorption suggests that solvation processes may be involved in these changes of absorption. The plots of the absorption vs. the volume fraction of DCA do not show any absorption maximum. This indicates that the ultrasonic absorption is not sensitive to the helix–coil equilibrium of PBLA in the frequency range investigated. A maximum value of 109S−1has been obtained for the rate constant of gro