Structure and Rheology of Solutions and Gels of Stiff Polyelectrolyte at High Salt Concentrationстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 3 октября 2016 г.
Аннотация:The rheology and the structural evolution of xanthan solutions and gels upon increasing polymer concentration were monitored in the absence and in the presence of cross-linker (chromium chloride). Direct visualization of the unperturbed structure of these systems by freeze-fracture transmission electron microscopy revealed the microphase-separated morphology with percolated polymer skeleton composed of aggregated chains. The thickness of the skeleton increases with increasing polymer concentration and at the addition of cross-linker, indicating enhancement of microphase separation. Upon cross-linking, the networks acquire higher plateau modulus G′, but it becomes less dependent on polymer concentration C than in the un-cross-linked state (G′ ∼ C1.35 and G′ ∼ C2.1, respectively). The molecular imaging also unraveled the presence of backfolded xanthan segments and many sharp
kinks at distances smaller than the persistence length, suggesting the presence of flexible hinges between double-helical fragments of the polysaccharide, which is in agreement with small-angle X-ray scattering data.