Institute of Molecular Physics, Polish Academy of Sciences, Poznań, Poland.
Langmuir. 2012 Oct 2;28(39):14039-44. doi: 10.1021/la302364d. Epub 2012 Sep 17.
The paper presents the diffusive diffraction phenomenon observed by the single-pulse-gradient spin-echo (s-PGSE) NMR technique in a real porous material: a gel composed of low-molecular-mass gelator methyl-4,6-O-(p-nitrobenzylidene)-α-D-glucopyranoside and toluene. Thanks to this phenomenon, we can probe the true microstructure (not xerogel) in which the toluene diffuses. To analyze the measured diffusion-diffraction pattern, we employed a composite bicompartmental model that superimposes restricted diffusion in small cavities of the gel matrix within the bundles of crossing fibers, with free diffusion in large and unconfined compartments between the bundles of crossing fibers. For restricted diffusion a pore-hopping formalism was applied. The observation of the diffraction pattern and its analysis leads to the conclusion that the pores, in the slow diffusing compartment of studied gel are ordered, at least locally, and relatively monodisperse with a size of 64 μm. Moreover, the restricting walls formed by the crossing fibers are perpendicular to the direction of the diffusion gradient.
本文通过单脉冲梯度自旋回波（s-PGSE）NMR 技术在真实多孔材料（由低分子量凝胶剂 4,6-O-（对硝基苯亚甲基）-α-D-吡喃葡萄糖甲酯和甲苯组成的凝胶）中观察到扩散衍射现象。得益于这一现象，我们可以探测到甲苯扩散的真实微观结构（非干凝胶）。为了分析测量的扩散-衍射模式，我们采用了一种组合的双隔室模型，该模型将在交叉纤维束内的凝胶基质小腔内的受限扩散与在交叉纤维束之间的大而无约束的隔室中的自由扩散叠加在一起。对于受限扩散，采用了孔跳跃形式。观察衍射图案及其分析得出的结论是，在研究的凝胶慢扩散隔室中的孔是有序的，至少在局部是有序的，并且相对单分散，尺寸为 64 μm。此外，由交叉纤维形成的限制壁垂直于扩散梯度的方向。
