DIRECT ELECTRON-TO-CARBON POLARIZATION TRANSFER IN HOMOGENEOUSLY DOPED POLYCARBONATES
DIRECT ELECTRON-TO-CARBON POLARIZATION TRANSFER IN HOMOGENEOUSLY DOPED POLYCARBONATES
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DOI：
10.1021/ma00042a009
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发表时间：
1992-08-03
期刊：
影响因子：
5.5
通讯作者：
SCHAEFER, J
中科院分区：
文献类型：
--
作者：
AFEWORKI, M;VEGA, S;SCHAEFER, J
对于均匀掺杂BDPA的聚碳酸酯的芳族和羰基碳，观察到直接的电子到碳的DNP固体效应极化转移（注释参见先前的论文）。直接电子到碳的极化转移在30-60埃的范围内进行。最接近自由基的碳首先被极化，并且具有最长的自旋-晶格弛豫时间。傅立叶变换的时域磁化，同步检测下的组合化学位移和C-H偶极相互作用，显示在偶极频率维度的不对称边带图案。定性同意所观察到的不对称边带图案的模拟，通过假设在附近的大体积的自由基的分子运动减少。
A direct electron-to-carbon DNP solid-effect polarization transfer is observed for the aromatic and carbonyl carbons of polycarbonate homogeneously doped with BDPA (see previous papers for notation). The direct electron-to-carbon polarization transfer operates over a range of 30-60 angstrom. Carbons that are closest to the free radicals are polarized first and have the longest spin-lattice relaxation times. Fourier transforms of time-domain magnetization, synchronously detected under combined chemical-shift and C-H dipolar interactions, show an asymmetrical sideband pattern in the dipolar frequency dimension. Simulations that qualitatively agree with the observed asymmetrical sideband patterns are obtained by assuming that molecular motion in the vicinity of the bulky free radical is reduced.