Configurational dependences of carbon-13 and proton NMR spin-lattice relaxation times of various polymethacrylates
Configurational dependences of carbon-13 and proton NMR spin-lattice relaxation times of various polymethacrylates
复制标题
各种聚甲基丙烯酸酯的碳 13 和质子 NMR 自旋晶格弛豫时间的构型依赖性
DOI：
10.1002/macp.1978.021790223
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发表时间：
1978
影响因子：
2.5
通讯作者：
H. Yuki
中科院分区：
文献类型：
--
作者：
K. Hatada;T. Kitayama;Y. Okamoto;K. Ohta;Y. Umemura;H. Yuki
采用阴离子法制备了等规聚间规聚甲基丙烯酸烷基酯S(R=CH3，C2H5，isC3H7，n-C4H9和t-C4H9)，并用反相恢复傅立叶变换(IRFT)方法测定了各碳和质子的自旋晶格弛豫时间t1。全同立构聚合物中碳的T1‘S始终长于间同立构聚合物中的可比碳。间同立构聚合物和全同立构聚合物的~(13)C-T_1‘S的比值始终在0、4~0、6的范围内。两种聚合物的~(13)C-T_1‘S均随酯基团体积增大而减小。从核Overhauser增强(NOE)的测量中发现，聚甲基丙烯酸酯中碳的自旋-晶格弛豫由13C-1H偶极相互作用主导，并且至少在70℃以上满足极窄条件。还研究了溶剂对13C-t1的影响。1H-T1‘S的测量结果与碳的测量结果是平行的。结果表明，t1对聚合物构型的依赖性主要是由聚合物链段迁移率的构型依赖性引起的。
Isotactic and syndiotactic poly(alkyl methacrylate)s (R = CH3, C2H5, isoC3H7, n-C4H9 and t-C4H9) were prepared by anionic mechanism and the spin-lattice relaxation times T1 of individual carbons and protons were measured mainly in toluene-d8 by the inversion-recovery Fourier transform (IRFT) method. The T1's of the carbons in the isotactic polymers were consistently longer than those of the comparable carbons in the syndiotactic polymers. The ratios of 13C-T1's for syndiotactic and isotactic polymers were always in the range of ca. 0,4–0,6 for all types of carbons. The 13C-T1's decreased with an increase in the bulkiness of the ester group in both polymers. From the measurements of the nuclear Overhauser enhancement (NOE) it was found that the spin-lattice relaxations of carbons in polymethacrylates are dominated by 13C-1H dipolar interactions and that the extreme narrowing condition is satisfied at least above 70°C. The effect of solvent on 13C-T1 was also studied. The results of the measurements of 1H-T1's were parallel to those in the carbons' case. It was concluded that the dependence of T1 upon the configuration of the polymer is mainly caused by the configurational dependence of the segmental mobility of the polymer.