Low frequency (105) shear elasticity of conventional and polymer fluids

The results of the study of low-frequency (105 Hz) shear elasticity of ordinary and polymer liquids are presented. It is assumed that the low-frequency viscoelastic relaxation of liquids is caused by the decay and recovery of fluctuation clusters. The cluster decays, apparently, by a «bound molecule - free molecule» transition, which resembles thedisintegration of a liquid drop due to the evaporation of individual molecules. The multistage process is characterized by a long relaxation time. The cluster lifetime is long, not because of the large kinetic units, but because of the large number of bound molecules that make up the cluster. Due to the rather long lifetime, the cluster does not have time to react to external low-frequency influences, which means that the liquid exhibits elastic properties at low frequencies. To explain this process, a cluster model of the fluid structure is proposed. The preliminary estimation carried out within the framework of the cluster model leads to a relatively high value of the average number of kinetic units included in the cluster. Apparently, viscoelastic relaxation in liquids refers to low-energy physical processes.