1,2-聚丁二烯分子运动的~(13)C-NMR研究——Ⅱ.分子运动的温度依赖性

本文用200MHz脉冲傅利叶变换波谱仪测定了1,2-聚丁二烯样品在不同温度下的~(13)C-T_(19)NOE,线宽和化学位移等~(13)G自旋弛豫参数,研究了1,2-聚丁二烯分子运动的温度依赖性.结果发现,在-10—-30℃之间,样品中各碳核的NOE和谱线宽度随温度变化的曲线斜率增加,表明此时长程链运动冻结;各碳核nT_1随温度的变化均在-45℃左右出现极小值.

13C-NMR STUDY ON MOLECULAR MOTION OF 1,2- POLYBUJADIENE II. Temperature Dependence of Molecular Motion

Proton-decoupled, 13C-NMR (operating at 50.3 MHz) is used to determine spin-lattice relaxation time (T1), Nuclear Overhauser Enhancement (NOE), line width and Chemical shift of 1,2-polybutadiene at different temperatures in CDCl3 solution and the temperature dependence of molecular motion of 1,2-polybutadiene is studied with these 13C-spin relaxation parameters. It is found that an increase of NOE and of the slope of the plot of line width vs. temperature appears at a range of -10-30℃ and this implied that long-range chain motion is frozen in this temperature range which is consistent with that of glass transition of the sample. The minimum values of curve of nT1 vs. temperature for all carbons occur at about -45℃.