REPTATION IN POLYMER BLENDS

Forward recoil spectrometry (FRES) was used to measure the tracer diffusion coefficients D*PS and D*PXE of deuterated polystyrene (d-PS) and deuterated poly(xylenyl ether) (d-PXE) chains in high molecular weight protonated blends of these polymers. The D*s were shown to be independent of matrix molecular weights and to decrease as M-2, where M is the tracer molecular weight, suggesting that the tracer diffusion of both species occurs by reptation. These D*s were used to determine the monomeric friction coefficients ζ0,PS and ζ0,PXE of the individual PS and PXE macromolecules as a function of f{cyrillic}, the volume fraction of PS in the PS:PXE blend. Since ζ0,PS≪ζ0,PXE at each f{cyrillic}, the rate at which a PS molecule reptates is much greater than that of a PXE molecule, even though both chains are diffusing in identical surroundings. Part of this difference may be due to the difficulty of backbone bond rotation of the PXE molecule. However, even when measured at a constant temperature increment above the glass transition temperature, ζ0,PS and ζ0,PXE were observed to be markedly composition dependent. In addition the ratio ζ0,PS ζ0,PXE varied from a maximum of 4 × 10-2 near f{cyrillic}=0.85 to a minimum of 5 × 10-5 for f{cyrillic}=0.0. These results show that intramolecular barriers do not solely determine the ζ0s of the components in this blend. Clearly, the interactions between the diffusing chains and the matrix chains also influence ζ0. © 1990.