6533b826fe1ef96bd1283a60

RESEARCH PRODUCT

Equilibrium phase behavior of polyethylene oxide and of its mixtures with tetrahydronaphthalene or/and poly(ethylene oxide-block-dimethylsiloxane)

subject

description

Liquid/solid and liquid/liquid (LL) transition temperatures were measured by means of an automated device that monitors the light passing through the systems as a function of T at different constant cooling or heating rates q. For pure polyethylene oxide (PEO) crystallization and melting temperatures depend on |q|0.3 and become identical at the equilibrium transition temperature Tm=61.0 °C in the limit of infinitely slow cooling/heating. The reduction of Tm for PEO dissolved in tetrahydronaphthalene (THN) yields information on the Flory–Huggins interaction parameter ξ between these two compounds; ξ results negative and decreases markedly with rising polymer concentration. A tentative explanation for this finding is offered. The binary blend between PEO and poly(ethylene oxide-block-dimethylsiloxane) (COP, Tm=0 °C) exhibits a much more complex phase diagram than the system THN/PEO. An additional and extended miscibility gap (LL) is observed at high temperatures and there is no experimental evidence of an...