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根据不同的跃迁运动和自由扩散运动模型导出了魔角旋转条件下的平均谱密度函数。从CP/MAS谱计算了样品中交联剂DVB的含量。依据实验测得的T_1值计算了一系列用DVB交联的聚甲基丙烯酸甲酯中x-甲基的转动相关时间以及扩散系数。结果表明:(1)随交联剂DVB含量的增加,相关时间增加,而扩散系数下降;(2)x-甲基的转动活化能与交联剂DVB无关,并且小于从介电和力学松弛所得的值。
The average spectral density function under the magic angle rotation is derived according to different transitional movement and free diffusion model. The content of crosslinker DVB in the sample was calculated from the CP / MAS spectra. Based on the experimentally measured T 1 values, the rotational correlation times and diffusion coefficients of x-methyl groups in a series of crosslinked polymethylmethacrylates with DVB were calculated. The results show that: (1) With the increase of the content of DVB, the related time increases and the diffusion coefficient decreases; (2) The rotational activation energy of x-methyl group has nothing to do with crosslinker DVB and less than that from dielectric and mechanical relaxation The value obtained.