Waters Dale J, Frank Curtis W
Department of Chemical Engineering, Stanford University, 381 North-South Mall, Stauffer III, Stanford, CA 94305-5025, United States.
Polymer (Guildf). 2009 Dec 10;50(26):6331-6339. doi: 10.1016/j.polymer.2009.05.034.
Diffusion coefficients of small oligosaccharides within high strength poly(ethylene glycol)/poly(acrylic acid) interpenetrating network (PEG/PAA IPN) hydrogels were measured by diffusion through hydrogel slabs. The ability of hindered diffusion models previously presented in the literature to fit the experimental data is examined. A model based solely on effects due to hydrodynamics is compared to a model based solely on solute obstruction. To examine the effect of polymer volume fraction on the observed diffusion coefficients, the equilibrium volume fraction of polymer in PEG/PAA IPNs was systematically varied by changing the initial PEG polymer concentration in hydrogel precursor solutions from 20 to 50 wt./wt.%. To examine the effect of solute radius on the observed diffusion coefficients, solute radii were varied from 3.3 to 5.1 Å by measuring diffusion coefficients of glucose, a monosaccharide; maltose, a disaccharide; and maltotriose, a trisaccharide. Both the hydrodynamic and obstruction models rely on scaling relationships to predict diffusion coefficients. The proper scaling relationship for each of the hindered diffusion models is evaluated based on fits to experimental data. The scaling relationship employed is found to have a greater significance for the hydrodynamic model than the obstruction model. Regardless of the scaling relationship employed, the obstruction model provides a better fit to our experimental data than the hydrodynamic model.
通过水凝胶平板扩散法测量了小寡糖在高强度聚（乙二醇）/聚（丙烯酸）互穿网络（PEG/PAA IPN）水凝胶中的扩散系数。检验了文献中先前提出的受阻扩散模型拟合实验数据的能力。将仅基于流体动力学效应的模型与仅基于溶质阻碍的模型进行了比较。为了研究聚合物体积分数对观察到的扩散系数的影响，通过将水凝胶前体溶液中初始PEG聚合物浓度从20 wt./wt.% 系统地变化到50 wt./wt.%，来改变PEG/PAA IPN中聚合物的平衡体积分数。为了研究溶质半径对观察到的扩散系数的影响，通过测量葡萄糖（一种单糖）、麦芽糖（一种二糖）和麦芽三糖（一种三糖）的扩散系数，使溶质半径在3.3至5.1 Å之间变化。流体动力学模型和阻碍模型都依赖于标度关系来预测扩散系数。基于对实验数据的拟合，评估了每个受阻扩散模型的适当标度关系。发现所采用的标度关系对流体动力学模型的意义比对阻碍模型更大。无论采用何种标度关系，阻碍模型对我们的实验数据的拟合都比流体动力学模型更好。
