DYNAMICS OF LINEAR AND STAR POLY(OXYPROPYLENE) STUDIED BY DIELECTRIC-SPECTROSCOPY AND RHEOLOGY

We give a quantitative comparison of dielectric and viscoelastic relax ation of identical poly(oxypropylene) (POP) diols and triols with mola r masses in the range 260-11 000 g/mol. The segmental relaxation probe d in dielectric spectroscopy (DS) is slower by a factor of 8 +/- 1, wh ile the conformational relaxation of the whole chain is faster by a fa ctor of 2.5 +/- 0.5. The molar mass dependence of the conformational r elaxation is close to the prediction of the Rouse model. POP diol with molar mass larger than 4000 g/L shows the influence of entanglement. A ''fast'' beta-relaxation with Arrhenius temperature dependence is ob served in all samples by DS. Measurements made on very low molar mass samples show that hydroxyl end groups are involved in this relaxation.