Compressibility of Colloids. 2. Compressibility Studies of Tri-Block Non-Ionic Polymers in Toluene and Water Solutions

摘要

Ultrasonic velocity measurements were made on a series of Pluronics i.e., tri-block non-ionic co-polymers of poly(ethylene oxide) poly(propylene oxide) poly(ethylene oxide) in solvents showing near ideal and non-ideal behavior. Aqueous solutions of the Pluronics studied show non-ideal behavior;-namely non-linear apparent compressibilty as a function of Pluronic concentration. This nonideality is thought to arise from aggregate formation. This is confirmed by laser light scattering measurements. Those polymers that dissolved in toluene showed near ideal behavior enabling us to determine intrinsic compressibilties of hydrophobic and hydrophilic blocks as 4.9 x 10 to the minus 11th power dyn/sq cm 2 and 3.9x10 to the minus the 11th power dyn/sq cm 2 respectively. The volume fraction of the bound water per segment of poly(ethylene oxide) is estimated and found to be dependent on the segment population. The mathematical treatment presented in this paper stems from that of Shiio, but goes further to define possible limits to the true compressibility, volume and density of bound water rather than making the assumption that no contraction of the water occurs. (Author)