在CP/MAS条件下交联聚甲基丙烯酸甲酯中α-甲基的^(13)C自旋-晶格弛豫(英文)

^(13)C SPIN-LATTICE RELAXATION OF α-CH_3 IN CROSSLINKED POLY (METHYL METHACRYLATES ) USING CP/MAS TECHNIQUES

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 functions under MAS condition were derived from various models of jump motion and models of freely diffusive motion. The contents of eras si inking agent DVB were evaluated by using CP/MAS spectra. The rotational correlation times and diffusion coefficients of a-CH, in a series of poly (methyl methacrylates) crosslinked with DVB were calculated according to the measured T, values. The results showed that: (1) the correlation times increase and the diffusion coefficients decrease as the contents of DVB increase, (2)the rotation activation energy of the a-CH., is independent of the contents of DVB and less than that from dielectric and mechanical relaxations.