Viscoelastic terminal relaxation behavior of unentangled polymers having hydrogen bonding moieties was examined. Specifically, partially saponified poly(vinyl acetate), i.e., poly(vinyl acetate-co-vinyl alcohol) with various hydroxyl (OH) group contents, f OH , was used as a model polymer. Formation of hydrogen bonds due to the presence of the OH groups resulted in the increase of both the glass transition temperature, T g , and the terminal relaxation time, τ w. For the viscoelastic spectra of all the samples, time-temperature superposition principle approximately held. The shift factors could be expressed by the universal Williams Landel Ferry equation by setting appropriate reference temperatures, T r *. Comparison of τ w under an iso-frictional condition (at T r *) revealed the formation of aggregates of constituent polymers. By considering the distribution of the aggregation numbers predicted by the mean field percolation model the viscoelastic spectra could be reproduced when f OH ≤ 0.28. However, for the samples with f OH = 0.35 and 0.37, an extra relaxation component was found to exist in addition to the prediction of the percolation model.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.