Multiple Dynamic Processes Contribute to the Complex Steady Shear Behavior of Cross-Linked Supramolecular Networks of Semidilute Entangled Polymer Solutions.
作者：Donghua Xu and Stephen L. Craig*.
關(guān)鍵字：///
論文來(lái)源：期刊
具體來(lái)源：The Journal of Physical Chemistry Letters 2010, 1,1683-1686.
發(fā)表時(shí)間：2010年
Molecular theories of shear thickening and shear thinning in associative
polymer networks are typically united in that they involve a single kinetic
parameter that describes the network ; a relaxation time that is related to the
lifetime of the associative bonds. Here we report the steady-shear behavior of two
structurally identical metallo-supramolecular polymer networks, for which singlerelaxation
parameter models break down in dramatic fashion. The networks are
formed by the addition of reversible cross-linkers to semidilute entangled solutions
of poly(4-vinylpyridine) (PVP) in dimethylsulfoxide (DMSO), and they differ only in
the lifetime of the reversible cross-links. Shear thickening is observed for crosslinkers
that have a slower dissociation rate (17 s-1), while shear thinning is
observed for samples that have a faster dissociation rate (ca. 1400 s-1). The
difference in the steady shear behavior of the unentangled versus entangled
regime reveals an unexpected, additional competing relaxation, ascribed to
topological disentanglement in the semidilute entangled regime that contributes
to the rheological properties.