Relationship between swelling and the electrohydrodynamic properties of functionalized carboxymethyldextran macromolecules.
Relationship between swelling and the electrohydrodynamic properties of functionalized carboxymethyldextran macromolecules.
复制标题
功能化羧甲基葡聚糖大分子的溶胀与电流体动力学特性之间的关系。
DOI：
10.1021/la700427p
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
J. Duval
中科院分区：
文献类型：
--
作者：
E. Rotureau;F. Thomas;J. Duval
研究了一种定义明确的功能化羧甲基葡聚糖（CMD）多糖在纳米3水溶液中广泛离子强度范围内的静电、水动力学和溶胀特性。通过结合原解滴定、动态光散射和电动力学分析，彻底研究了CMD大分子的聚羧酸电荷和摩尔质量对其电流体动力学特性的影响。在足够高的电解质浓度下获得的电泳迁移率数据揭示了典型的软颗粒行为。随着离子强度的降低，迁移率显著增加，同时静电膨胀明显，扩散系数降低。CMD实体经历了构象转变，从大离子强度下的紧凑随机线圈到低NaNO3浓度下的肿胀线圈和可能的蠕虫状结构。尺寸和迁移率随电解质浓度变化的幅度很大程度上取决于CMD实体的总电荷以及它的摩尔质量。这些因素控制了组成聚合物链的刚度，从而控制了大分子的渗透程度（“柔软度”）。利用先前为带电可渗透大分子的电流体动力学开发的软扩散界面形式，对电泳迁移率数据进行了定量分析。扩散系数和空间电荷密度伽玛度的测量值，作为独立于电位滴定曲线的建模评估，被考虑在一个自一致的方式。研究发现，低电荷密度的大CMD实体对流动渗透的渗透性最强，且链的非均质静电硬化程度有限，而伽马度较大的小CMD实体在离子强度降低时显著膨胀，导致聚合物链密度的空间分布具有很强的各向异性。
The electrostatic, hydrodynamic, and swelling properties of a well-defined, functionalized carboxymethyldextran (CMD) polysaccharide are investigated in aqueous NaNO3 solution over a broad ionic strength range. The impact of the polycarboxylate charge and molar mass of the CMD macromolecules on their electrohydrodynamic features is thoroughly examined by combined protolytic titration, dynamic light scattering, and electrokinetic analyses. Electrophoretic mobility data obtained for sufficiently high electrolyte concentrations reveal a typical soft particle behavior. Upon decrease of the ionic strength, mobilities strongly increase in magnitude while significant electrostatic swelling takes place, as reflected in a decrease in the diffusion coefficients. CMD entities undergo conformational transitions from compact random coil at large ionic strengths to swollen coil and possibly a wormlike structure at lower NaNO3 concentrations. The magnitude of the variations in size and mobility with electrolyte concentration strongly depends on the overall charge of the CMD entity as well as on its molar mass. These factors control the stiffness of the constituent polymer chains and thus the degree of macromolecular permeability ("softness"). Using the soft-diffuse interface formalism previously developed for the electrohydrodynamics of charged permeable macromolecules, a quantitative analysis of the electrophoretic mobility data is presented. The measured values of the diffusion coefficient and space charge density Gamma degrees, as evaluated independently from the modeling of potentiometric titration curves, are taken into account in a self-consistent manner. It is found that large CMD entities of low charge densities are the most permeable to flow penetration with a limited heterogeneous electrostatic stiffening of the chains, whereas small CMD entities of larger Gamma degrees significantly expand upon lowering the ionic strength, giving rise to a strong anisotropy for the spatial distribution of polymer chain density.