Entanglement in miscible blends

The entanglement length $L_{\mathrm{e}}$ of polymer chains (corresponding to the entanglement molecular weight $M_{\mathrm{e}}$) is not an intrinsic material parameter but changes with the interaction with surrounding chains. For miscible blends of \textit{cis}-polyisoprene (PI) and poly(\textit{tert}-butyl styrene) (PtBS), changes of $L_{\mathrm{e}}$ on blending was examined. It turned out that the Le averaged over the number fractions of the Kuhn segments of the components (PI and PtBS) satisfactorily describes the viscoelastic behavior of pseudo-monodisperse blends in which the terminal relaxation time is the same for PI and PtBS.