Segmental Dynamics of Dilute Poly(ethylene oxide) in Low and High Molecular Weight Glass-Formers

Abstract

Deuterium NMR at Larmor frequencies of 15.6 and 76.7 MHz was used to study the segmental dynamics of dilute perdeuteriopoly(ethylene oxide) (d4PEO) in equilibrium miscible mixtures with four low molecular weight glass-formers: indomethacin, sucrose benzoate, o-terphenyl, and toluene. Results are compared with literature data for dilute PEO in two polymer hosts: poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc). The segmental dynamics of PEO are found to strongly correlate with the dynamics of both high and low molecular weight hosts. For dilute PEO in mixtures with PMMA, PVAc, and sucrose benzoate, the Lodge–McLeish model with a ϕself (self-concentration) of 0.35 gives a good fit to the dynamics of dilute PEO, similar to previously reported dilute polyisoprene blends and dilute polystyrene blends. A smaller ϕself is obtained for dilute PEO in indomethacin, consistent with the presence of a hydrogen-bonding effect. For PEO in o-terphenyl and toluene, the implementation of the Lodge–McLeish model utilized here fails to give quantitative fits for the dynamics of the dilute PEO chains; this result is obtained because the full temperature-dependent host dynamics are not utilized in the fitting procedure.