【摘要】 该文以2种不同立构聚丙烯(iPP和sPP)为讨论对象,首先研究了量化计算方法在预测高分子13C各向同性和各向异性化学位移(CSA)中的应用,然后讨论了近年来发展的测定13C CSA粉末线形的2种重要固体NMR实验技术(SUPER和RAI)的特点和实验优化问题.最后,利用可获得接近无扭曲线形的SUPER技术测定了等规立构聚丙烯样品的13C CSA粉末线形,并与量化计算理论结果比较.结果表明:13C各向同性化学位移及CSA粉末线形的理论计算结果均与固体NMR实验结果有很好的符合,预示通过13C CSA量化计算结合固体NMR实验是阐明高分子微观结构的有力工具.更多还原

【Abstract】 Chemical shift isotropy and anisotropy of isotactic and syndiotactic polypropylene(denoted as iPP and sPP,respectively) were predicted by quantum chemical calculation.13C chemical shift anisotropy(CSA) powder patterns of iPP were successfully determined with the separation of undistorted powder patterns by effortless recoupling(SUPER) experiments.It was found that the results from quantum chemical calculation are in good accordance with that from solid-state NMR experiments.These results indicate that the combination of quantum chemical calculation and solid-state NMR experiment is a powerful tool in elucidating the microstructure of polymers.The two important solid-state NMR techniques for obtaining 13C CSA powder pattern,SUPER and recoupling of anisotropy information(RAI),were compared,with their advantages and disadvantages discussed using methylmalonic acid as a sample compound.更多还原