Some Examples

Continuity at negativepressure ( -solvent poor-solvent transitions). Imre and Van Hook used the Berthelot technique to generate negative pressures in order to induce phase transitions in some different polymer solvent systems. 17 In PS propionitrile, PS PPN, PPN a poor solvent, they demonstrated continuity for the demixing curve across P 0 and well into the region P< 0. It is the choice of solvent quality which dictates whether the hypercritical point lies at P> 0, P 0, or P< 0. In...

The Cohesive Energy Density Of Polymer Liquids

DuPont Experimental Station Wilmington, DE, USA One of the most important thermodynamic properties of a liquid is its cohesive energy density (CED). It is the energy per unit volume of the liquid required to move a molecule from the liquid state to a vapor state. It is a measure of the interactions between the molecules in the liquid state. The CED is defined as the ratio of the molar energy of vaporization (AU) divided by the molar liquid volume (V). Polymer molecules have a vanishingly small...

Experimental Observations Of Nonequilibrium Concentration Fluctuations In A Polymer Solution

Light-scattering experiments in solutions of polystyrene with mass-averaged molecular weight M w 96,400 dissolved in toluene have been performed in our laboratory. The polystyrene solution was contained in a horizontal layer located between an upper and lower plate. The optical arrangement was similar to the one used earlier for measuring nonequilibrium fluctuations in liquid mixtures of toluene and n-hexane 9 . Because of the dependence of the nonequilibrium enhancement of the fluctuations on...