Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
J Phys Chem B. 2011 Apr 28;115(16):4613-20. doi: 10.1021/jp112390d. Epub 2011 Apr 6.
Dendrimers are attractive templates to display functional molecular components. Since the behavior of dendrimer systems can depend greatly on the accessibility of these molecular components to the external environment, and on the spatial arrangement of functional groups attached to the dendrimer terminal branches (end-groups), techniques to determine the locations of end-groups are highly desirable. In this report, we describe a method to analyze the EPR spectra of multiple generations of poly(amidoamine) (PAMAM) dendrimers which have spin-labels attached to end-groups in variable percentages of the total number of available sites. The spectra are treated as a convolution of a narrow spin-label spectrum and a variable line broadening function. Trends in the parameters that describe the best-fit line broadening function with spin-label loading reveal the spatial arrangements and homogeneity of spin environments of the labels. We observe a shift in the end-group distribution from generation 3 (G(3)) to G(4) dendrimers that indicates a change in morphology from an open, extended structure to a more dense, compact arrangement.
树状聚合物是展示功能分子组件的有吸引力的模板。由于树状聚合物系统的行为在很大程度上取决于这些分子组件对外部环境的可及性，以及连接在树状聚合物末端支链（端基）上的官能团的空间排列，因此确定端基位置的技术是非常需要的。在本报告中，我们描述了一种分析具有不同百分比的可及性的端基上的自旋标记的多代聚（酰胺-胺）（PAMAM）树状聚合物的 EPR 光谱的方法。这些光谱被视为窄自旋标记光谱和可变线宽函数的卷积。描述最佳拟合线宽函数的参数随自旋标记负载的变化趋势揭示了标记的自旋环境的空间排列和均匀性。我们观察到从第三代（G(3)）到第四代（G(4)）树状聚合物的端基分布的移动，这表明形态从开放、扩展结构转变为更密集、紧凑的排列。
