VOLUMETRIC PROPERTIES OF AQUEOUS-SOLUTIONS OF TRIBLOCK (PEP) COPOLYMERS OF ETHYLENE-OXIDE AND PROPYLENE-OXIDE

Specific volumes of aqueous solutions of triblock (PEP) copolymers of ethylene oxide and propylene oxide at solute weight fractions 0.1 less than or equal to w(2) less than or equal to 0.39 were measured in the temperature range from 5 to 65 degrees C. Partial molar volumes (V) o ver bar(2) per chain repeat unit, their temperature quotient partial d erivative (V) over bar(2)\partial derivative T, and excess partial mol ar volumes (V) over bar(2)(E) were computed. The values of (V) over ba r(2), partial derivative (V) over bar(2)/partial derivative T and the absolute values \(V) over bar(2)(E)\ decrease with increasing content of ethylene oxide units. The excess partial molar expansibility <(alph a)over bar>(0E)(2) at infinite dilution for oligomeric homopolymers (P EO, PPO) were evaluated from reported data. They are positive and disp lay a similar trend to \(V) over bar(2)(E)\. The values of (V) over ba r(2) and <(alpha)over bar>(0E)(2) are comparable to those reported for low-molecular-weight cyclic ethers. The results are taken to reflect the effects of polar and apolar groups on the supermolecular structure of water.