Zhou Zhe, Kümmerle Rainer, Stevens James C, Redwine David, He Yiyong, Qiu Xiaohua, Cong Rongjuan, Klosin Jerzy, Montañez Nikki, Roof Gordon
The Dow Chemical Company, Freeport, TX 77541, USA.
J Magn Reson. 2009 Oct;200(2):328-33. doi: 10.1016/j.jmr.2009.07.017. Epub 2009 Jul 18.
Recently, a high temperature 10 mm cryoprobe was developed. This probe provides a significant sensitivity enhancement for (13)C NMR of polyolefins at a sample temperature of 120-135 degrees C, as compared to conventional probes. This greatly increases the speed of NMR studies of comonomer content, sequence distribution, stereo- and regioerrors, saturated chain end, unsaturation, and diffusion of polymers. In this contribution, we first compare the (13)C NMR sensitivity of this probe with conventional probes. Then, we demonstrate one of the advantages of this probe in its ability to perform 2D Incredible Natural Abundance Double Quantum Transfer Experiment (2D INADEQUATE) in a relatively short period of time. The 2D INADEQUATE has been rarely used for polymer studies because of its inherently very low sensitivity. It becomes even more challenging for studying infrequent polyolefin microstructures, as low probability microstructures represent a small fraction of carbons in the sample. Here, the 2D INADEQUATE experiment was used to assign the (13)C NMR peaks of 2,1-insertion regioerrors in a poly(propylene-co-1-octene) copolymer.
最近，一种高温10毫米低温探头被研发出来。与传统探头相比，该探头在120 - 135摄氏度的样品温度下，能显著提高聚烯烃的（13）C NMR灵敏度。这极大地提高了对聚合物共聚单体含量、序列分布、立体和区域错误、饱和链端、不饱和度以及扩散进行核磁共振研究的速度。在本论文中，我们首先将该探头的（13）C NMR灵敏度与传统探头进行比较。然后，我们展示了该探头的一个优势，即能够在相对较短的时间内进行二维难以置信的天然丰度双量子转移实验（2D INADEQUATE）。由于其固有的极低灵敏度，2D INADEQUATE很少用于聚合物研究。对于研究罕见的聚烯烃微观结构而言，这变得更具挑战性，因为低概率微观结构在样品中仅占一小部分碳。在此，2D INADEQUATE实验被用于确定聚（丙烯 - 共 - 1 - 辛烯）共聚物中2,1 - 插入区域错误的（13）C NMR峰。
