金属络合对黄原胶多糖溶液形态和流变学影响的建模,Macromolecules

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金属络合对黄原胶多糖溶液形态和流变学影响的建模
Macromolecules ( IF 5.1 ) Pub Date : 2021-09-13 , DOI: 10.1021/acs.macromol.1c01328
Kolattukudy P. Santo ₁ , Kristina I. Fabijanic ₂ , Chi-Yuan Cheng ₂ , Andrei Potanin ₂ , Alexander V. Neimark ₁

Affiliation

多糖溶液通常含有金属离子，金属离子与聚合物配体形成交联络合物，显着影响聚合物的形态和溶液流变学。在这里，我们通过多尺度计算模型与原子力显微镜 (AFM) 测量相辅相成，以含 ZnCl ₂的黄原胶 (XG) 溶液为例研究金属络合的分子机制. 我们开发了原始原子分子动力学 (MD) 和粗粒度耗散粒子动力学 (DPD) 模型，用于不同成分和 Zn 络合的 XG 链。MD 模拟表明，Zn 显着影响单个 XG 链的构象，通过形成各种类型的链内交联而导致回转半径减小，而链中丙酮酸含量的增加会增强这些交联。静态条件下和剪切流下的 DPD 模拟表明，由于链间交联的增强，盐的添加通过溶胶-凝胶转变导致 XG 系统中的凝胶化。剪切流中发生两种形态转变：XG 链在流动方向上对齐的向列相的取向转变和捆绑转变，伴随着高 Zn 浓度下的反向凝胶 - 溶胶转变。链中增加的丙酮酸含量的存在导致更强的聚集和更坚硬的聚集，这与 AFM 结果定性一致。所提出的模拟金属络合和链组成对形态和流变特性的影响的计算方法可以扩展并应用于各种多糖系统。

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Modeling of the Effects of Metal Complexation on the Morphology and Rheology of Xanthan Gum Polysaccharide Solutions

Polysaccharide solutions commonly contain metal ions, which form cross-linking complexes with polymer ligands and significantly affect the polymer morphology and solution rheology. Here, we study by multiscale computational modeling complemented with atomic force microscopy (AFM) measurements the molecular mechanisms of metal complexation with examples of xanthan gum (XG) solutions containing ZnCl₂. We develop original atomistic molecular dynamics (MD) and coarse-grained dissipative particle dynamics (DPD) models for XG chains of different compositions and Zn complexation. MD simulations reveal that Zn dramatically affects conformations of individual XG chains, causing a reduction in the radius of gyration by the formation of various types of intrachain cross-linking that are enhanced by the increased pyruvate content in the chains. DPD simulations at the static conditions and under the shear flow show that salt addition leads to gelation in XG systems via a sol–gel transition due to enhanced interchain cross-linking. Two morphological transitions occur in the shear flow: an orientational transition to a nematic phase with XG chains aligned in the direction of flow and a bundling transition accompanied by a reverse gel–sol transition at high Zn concentrations. The presence of the increased pyruvate content in the chains leads to stronger aggregation and stiffer aggregates, in qualitative agreement with AFM results. The proposed computational methodology of modeling the effects of metal complexation and chain composition on morphological and rheological properties may be extended and applied to various polysaccharide systems.

更新日期：2021-09-28

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