Temperature dependence of tracer diffusion coefficients in polystyrene

The temperature dependence of the tracer diffusion coefficient D* of long deuterated polystyrene (d-PS) chains of molecular weight M>M_c, where M_c is the critical molecular weight for entanglement, diffusing into highly entangled PS matrices, each of molecular weight P = 2×10⁷, is studied using forward recoil spectrometry. It is found that the temperature dependence of D*/T, reflected primarily in the monomeric friction coefficient, is accurately described by a Vogel equation. The constants that are used to fit these results are independent of M and are the same as those used to fit the temperature dependence of the zero shear rate viscosity of polystyrene.