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中文摘要：
以正己烷为探针分子,采用基于常梯度自旋回波序列的核磁共振技术（CFG-NMR）研究了小分子在SiO2颗粒和通过相转化法制备的SiO2/Poly（styrene-co-acrylic acid）（SiO2/PSA）复合颗粒中的扩散行为.根据双位点模型和分子交换的理论,采用两组分指数拟合实验得到的1H CFG NMR信号衰减曲线表明,正己烷在SiO2颗粒和SiO2/PSA颗粒中具有2个相差一个数量级的扩散系数.在相同的扩散时间下,正己烷在SiO2/PSA颗粒中的2个扩散系数均小于其在SiO2颗粒中的扩散系数,说明复合颗粒壳层的聚合物膜对正己烷的扩散具有阻碍作用.通过改变常梯度自旋回波序列中的扩散时间,研究了脉冲序列中扩散时间对扩散系数的影响,结果表明正己烷在复合粒子中的扩散系数强烈依赖于扩散时间的大小.
英文摘要：
The diffusion of n-hexane in SiO2 particles and SiO2/poly（styrene-co-acrylic acid）（SiO2/PSA） core-shell particles,prepared by phase inversion method,was investigated by constant gradient field NMR（CFG-NMR）.According to the two-site model and molecular exchange theory,1H CFG echo decay curves of n-hexane could be fit as biexponentials,implying that two different diffusion coefficients were existed in the diffusion system.The diffusion coefficients of n-hexane in the SiO2/PSA core-shell particles were much lower than in the SiO2 particles,indicating that the poly（styrene-acrylic acid） shell played as a barrier on the diffusion of n-hexane.By varying the diffusion time in the pulsed sequence,we found that the diffusion coefficients of n-hexane in the core-shell particles were strongly depended on the diffusion time.
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