Interplay between Microscopic and Macroscopic Properties of Charged Hydrogels,Macromolecules

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Interplay between Microscopic and Macroscopic Properties of Charged Hydrogels
Macromolecules ( IF 5.1 ) Pub Date : 2019-12-26 , DOI: 10.1021/acs.macromol.9b01824
Di Jia ₁ , Murugappan Muthukumar ₁

Affiliation

We have investigated aqueous charged poly(acrylamide-co-acrylate) gels by varying polymer concentrations at fixed concentrations of added sodium chloride salt. Using a combination of static and dynamic light scattering, rheology, and water permeation experiments, we have made independent measurements of shear modulus, friction coefficient, diffusion coefficient, and mesh size of the gel. We have also derived a generalized mean field theory for charged gels by including electrostatic interactions between polymer segments, in addition to the contributions from free energy of mixing, elasticity, and the Donnan equilibrium. The measured dependencies of modulus, friction coefficient, and gel diffusion coefficient on polymer concentration are in accordance with the predictions of the generalized mean field theory, enabling a reliable bridge between the macroscopic and microscopic properties of polyelectrolyte gels. When the contributions to free energy of the gel from fluctuations in polymer concentration and conformations are ignored, experimentally observed results self-consistently satisfy the scaling laws among mesh size, moduli, gel friction coefficient, and gel diffusion coefficient, with an effective polymer size exponent of 2/3 in the presence of salt. Our systematic observations suggest the validity and utility of closed-form analytical formulas from the generalized mean field theory to adequately describe swollen charged gels, while opening further work on determination of fluctuation effects.

中文翻译：

带电水凝胶的微观和宏观特性之间的相互作用

我们研究了带电的聚（丙烯酰胺-钴-丙烯酸酯）通过在固定浓度的氯化钠盐中改变聚合物浓度来凝胶化。通过结合静态和动态光散射，流变学和水渗透实验，我们对凝胶的剪切模量，摩擦系数，扩散系数和筛孔尺寸进行了独立测量。除了混合自由能，弹性和Donnan平衡的贡献之外，我们还通过包括聚合物链段之间的静电相互作用，得出了带电凝胶的广义平均场理论。测得的模量，摩擦系数和凝胶扩散系数与聚合物浓度的相关性符合广义平均场理论的预测，可以在聚电解质凝胶的宏观和微观特性之间建立可靠的桥梁。当忽略聚合物浓度和构象变化对凝胶自由能的贡献时，实验观察到的结果可以自洽地满足筛孔尺寸，模量，凝胶摩擦系数和凝胶扩散系数之间的比例定律，并具有有效的聚合物尺寸指数在盐的存在下为2/3。我们的系统观察表明，广义广义场理论的闭式分析公式的有效性和实用性足以充分描述溶胀的带电凝胶，同时为确定波动效应开辟了进一步的工作。实验观察到的结果一致地满足了筛孔尺寸，模量，凝胶摩擦系数和凝胶扩散系数之间的比例定律，在盐存在下有效的聚合物尺寸指数为2/3。我们的系统观察表明，广义广义场理论的闭式分析公式的有效性和实用性足以充分描述溶胀的带电凝胶，同时为确定波动效应开辟了进一步的工作。实验观察到的结果一致地满足了筛孔尺寸，模量，凝胶摩擦系数和凝胶扩散系数之间的比例定律，在盐存在下有效的聚合物尺寸指数为2/3。我们的系统观察表明，广义广义场理论的闭式分析公式的有效性和实用性足以充分描述溶胀的带电凝胶，同时为确定波动效应开辟了进一步的工作。

更新日期：2019-12-27

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