Using high resolution PFG NMR spectroscopy, we have studied the diffusion of well-characterized polymer rings in linear host matrices at various observation times Δ, varying both ring and host molecular weights. For the first time, to our knowledge, for higher M_w rings in entangled melts it was possible to directly distinguish two different diffusive modes: (i) fast diffusion that scales inversely with the host chain length and (ii) much slower diffusion depending much more strongly on the host molecular weight. Furthermore, we studied the diffusion of the linear chains in the host melts. The diffusion data were analyzed in terms of existing theories and compared to simulations. The two-mode structure directly verifies the hypothesis of qualitatively different mechanisms for ring diffusion in linear melts. The fast mode quantitatively agrees with the assertion of a special diffusion channel for once threaded rings, while the suggested diffusion of unthreaded rings was not found. The slow mode scales more weakly with the host chain length than predicted by the constraint release (CR) mechanism. However, considering an interdependence of constraints ( Macromolecules 1986, 19, 105), the slow mode was quantitatively related to tube renewal processes. Using this concept also the molecular weight dependence of the matrix diffusion is described naturally. In contrast to the explicit observation of fast and slow diffusive modes simulations reveal broadly distributed heterogeneities leading to a prevailing CR mechanism only. The strong size dependent ring diffusion in an entangled matrix remains unintelligible. Finally, even though we have distinguished two well-defined significantly different diffusive modes with characteristic times in the millisecond range that would be expected to interchange, a detailed analysis in terms of a two-state diffusion model allowing for state changes reveals that within the experimental sensitivity no such exchanges take place.

中文翻译：

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通过脉冲场梯度（PFG）NMR直接观察线性聚合物基质中聚合物环的两种不同的扩散模式

使用高分辨率PFG NMR光谱，我们研究了在各种观察时间Δ下，环和主体分子量均发生变化的，特征明确的聚合物环在线性主体基质中的扩散。据我们所知，这是第一次，更高的M _w在纠缠的熔体中形成环，可以直接区分两种不同的扩散模式：（i）与主体链长度成反比的快速扩散，以及（ii）取决于主体分子量的更慢的扩散。此外，我们研究了线性链在主体熔体中的扩散。根据现有理论分析了扩散数据，并与模拟进行了比较。双模结构直接验证了线性熔体中环扩散的定性机理不同的假设。快速模式在定量上与曾经有一个螺纹环的特殊扩散通道的主张相符，而未发现无螺纹环的建议扩散。慢速模式在宿主链长度上的缩放比约束释放（CR）机制所预测的弱得多。然而，大分子 1986年，19（105），慢速模式与试管更新过程定量相关。使用该概念，自然也描述了基体扩散的分子量依赖性。与快速和慢速扩散模式的显式观察相反，模拟揭示了广泛分布的异质性，仅导致普遍的CR机制。纠缠矩阵中依赖于大小的强环扩散仍然难以理解。最后，即使我们已经区分出两种定义明确的，显着不同的扩散模式，它们的特征时间在毫秒范围内，可以预期会互换，但针对允许状态变化的两态扩散模型进行的详细分析显示，在实验范围内敏感性，没有这样的交流发生。