Effect of the anisotropic chain motion in molten polymers: The solidlike contribution of the nonzero average dipolar coupling to NMR signals. Theoretical description
Effect of the anisotropic chain motion in molten polymers: The solidlike contribution of the nonzero average dipolar coupling to NMR signals. Theoretical description
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熔融聚合物中各向异性链运动的影响：非零平均偶极耦合对 NMR 信号的固体贡献。
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发表时间：
1974
期刊：
影响因子：
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通讯作者：
J. Cohen
中科院分区：
文献类型：
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作者：
J. Cohen
一个类似于Rouse提出的链涨落模型被用来描述熔融聚合物的NMR性质。作为一个单一的质子对的磁弛豫的一般属性，它示出的运动窄化近似内，非零平均偶极耦合引起的旋转框架中的两个组件的自由游行信号。一个是与脉冲射频场正交，就像普通液体中通常的那样。然而，它的时间演变是典型的存在一个非零平均偶极耦合。另一个与射频场同相，这在普通固体中很常见;它的振幅与质子对内偶极耦合的非零平均值成比例。它还表明，该组件可以观察到通过使用合适的脉冲序列已经提出了研究自旋系统在固体中。在相同的近似下，它表明，这样的质子对的高分辨率共振谱可能会强烈修改的存在下的…
A model of chain fluctuations analogous to that proposed by Rouse is used to describe NMR properties of molten polymers. As a general property of the magnetic relaxation of a single proton pair, it is shown that within the motional narrowing approximation, the nonzero average dipolar coupling gives rise to a free procession signal with two components in the rotating frame. One is in quadrature with the pulse radio‐frequency field, as is usual in ordinary liquids. However, its time evolution is typical of the presence of a nonzero average dipolar coupling. The other one is in phase with the rf field, as is usual in ordinary solids; its amplitude is proportional to the nonzero average of dipolar coupling within the proton pair. It is also shown that this component can be observed by using suitable pulse sequences already proposed to study spin systems in solids. In the same approximation, it is shown that the high resolution resonance spectrum of such a proton pair may be strongly modified in the presence o...