Enthalpy of interaction of crystalline poly(ethylene oxide) with water, toluene, and chloroform

The enthalpies of dissolution of crystalline PEO (M = 1.7 x 10(6)) and PEG (M = 3 x 10(3)) and the enthalpies of dilution of their homogeneous solutio ns and heterogeneous mixtures with water, toluene, and chloroform in excess of the corresponding solvents at 298 K were measured. The values of the en thalpy of mixing were calculated for the entire composition range, includin g the contributions from the component interaction and the destruction of c rystal lattice of semicrystalline polymers. A procedure fur the separation of these contributions based on the phase diagrams of mixtures and the valu es of the enthalpies of polymer fusion was proposed. The obtained values of the enthalpy of interaction of PEG and PEG with the solvents agree with th e published data on the enthalpy of mixing in the corresponding low-molecul ar-mass systems both in the sign and in the value of the change in enthalpy as well as in the pattern of its concentration dependence. The enthalpy of interaction is negative for the solutions in chloroform over the entire co mposition range and for the solutions in water and toluene at low and moder ate polymer concentrations. The exothermal effect of interaction increases upon passing from aqueous solutions to the solutions in toluene and chlorof orm as well as upon a decrease in the polymer molecular mass.