TEMPERATURE STUDY OF SOUND-VELOCITY AND VOLUME-RELATED SPECIFIC THERMODYNAMIC PROPERTIES OF AQUEOUS-SOLUTIONS OF POLY(ETHYLENE OXIDE) POLY(PROPYLENE OXIDE) POLY(ETHYLENE OXIDE) TRIBLOCK COPOLYMERS

A comprehensive study of sound velocity and apparent specific volume, and adiabatic compressibility and expansibility thermodynamic properti es of aqueous solutions of a number of POE-POP-POE triblock copolymers has been carried out in the temperature range 10-45 degrees C. Three series of the above block copolymers were studied: one having similar relative molar masses but different POP/POE mass ratios (F38, P103, P8 5); another having the same POP/POE mass ratio but different relative molar masses (L64, P84, P104 and F38, F68, F108); and a series in whic h the copolymers have the same absolute POP content but different rela tive molar masses (P103, P104, P108). An abrupt transition in the temp erature dependence of the volumetric and sound velocity properties occ urs in the temperature range 10-45 degrees C for many of the copolymer s. This is due to the self-aggregation of the copolymers. The results of this study show that the relative molar mass, POP/POE mass ratio an d POP content of the copolymers are factors that play a role in the se lf-aggregation of these systems. The extensive study of the sound velo city property of these systems extends and confirms the few previous r eports that it is a sensitive macroscopic probe of the onset of self-a ggregation processes in these systems. The apparent specific volume da ta of the copolymers has been used to test current models of these agg regates. The results show that the POP core contains some water. (C) 1 997 Academic Press.