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[摘要]：Molecular dynamics of it series of poly(ethylene glycol)-poly(amidoamine) (PEG-PAMAM) dendrimer blends and PEG conjugated PAMAM dendrimers were investigated and contrasted using broadband dielectric relaxation spectroscopy (DRS). The study was carried with 2000 Da PEG and generation 3 PAMAM dendrimers. The results were generated over a wide range of frequencies and temperatures. A number of relaxation processes were detected and their origin and characteristics established. PEG-dendrimer blends show three local processes and a segmental process contributed by the amorphous PEG. The time scale of segmental relaxation decreases with increasing concentration of dendrimers due to the H-bonding that forms between the PEG oxygen and the amino groups on the Surface of dendrimers. PEGylated dendrimers show two local processes and a segmental process, also contributed by the amorphous PEG. But unlike the blends, the amorphous PEG in PEGylated dendrimers is constrained not only by the crystalline lamellae but also by the covalent bonds with the dendrimer. This results in I different morphology which, in turn, gives rise to it different time scale of segmental relaxation in PEG-dendrimer blends and PEGylated dendrimers. A comprehensive analysis of the effect of morphology, concentration of dendrimers. number of attached PEG chains, and temperature on the relaxation time, dielectric relaxation strength, and spectral characteristics of various relaxation processes is offered. The results reported here are expected to provide an added dimension to our understanding of the principles that guide drug delivery concepts. |
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