| ASSIGNMENT OF ~(13)C-NMR SPECTRA OF POLYMER WITH SEMIEMPIRICAL METHOD——A STUDY OF VINYL TERTIARY CARBON IN 1,2-POLYBUTADIENE (1,2-PBD) |
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| 作者姓名： | 高原平 周子南 冯之榴 |
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| 作者单位： | Changchun Institute of Applied Chemistry，Academia Sinica，Changchun Institute of Applied Chemistry，Academia Sinica，Changchun Institute of Applied Chemistry，Academia Sinica |
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| 摘 要： | Matrix multiplication technique has been employed to calculate the probabilities of different rotational isomeric states of the bonds in the main chains of 1, 2-PBD. Using the relation that relative chemical shift is in proportion to the sum of bond probabilities which make contribution to the chemical shift of a certain carbon, a new assignment has been obtained directly from the sum of bond probabilities. According to the assignment, these pentads are mmmm, mmmr, rmmr, mmrr, mmrm, rmrr, rmrm, rrrr, mrrr and mrrm from downfield to upfield.In order to prove experimentally the result mentioned above, isotactic 1,2-PBD was successfully synthesized in our lab. The polymer is identified by the infrared spectroscopy, X-ray diffraction and differential scanning calorimetry. Comparison between the ~(13)C-NMR spectra of heterotactic and isotactic 1,2-PBD reveals that the first peak downfield in the former represents the pentad mmmm. Consequently, the assignment is in agreement with neither that of Elgert nor th
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| 关 键 词： | ~(13)C-NMR spectrum assignment semiempirical method simple system bond probability γ effect. |
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