关键词: 交叉极化, C₆₀/PEO复合物, 核磁共振, 相结构

Abstract:

A composite of poly (ethylene oxide) (PEO) and fullerene (C₆₀) was prepared by lyophilization, and studied by high-resolution solid-state NMR spectroscopy. The ¹H spin-spin relaxation time  (T₂) of the composite was measured by ¹H-¹³C cross-polarization experiments with different contact times. It was found that the choice of contact time influence the results of intermolecular cross-polarization experiments, implying that extra care should be taken to select appropriate contact time when applying the intermolecular crosspolarization method to study the phase structures of composites. On the other hand, variation of contact time may provide a new dimension for experimental design and be used to gain information that is not obtainable in conventional experiments with fixed contact time. For example, the results of our experiments showed that in the PEO/C₆₀ composite not all the fullerene molecules are confined in the noncrystalline region of PEO, at least a portion of the C₆₀ molecules are located close to the crystalline region.

Key words: solid-state NMR, phase structure, cross polarization, C₆₀/PEO composite