NATURE OF THE PROTON NMR TRANSVERSE RELAXATION FUNCTION OF POLYETHYLENE MELTS .1. MONODISPERSED POLYETHYLENES
NATURE OF THE PROTON NMR TRANSVERSE RELAXATION FUNCTION OF POLYETHYLENE MELTS .1. MONODISPERSED POLYETHYLENES
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DOI：
10.1021/ma00008a055
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发表时间：
1991-04-15
期刊：
影响因子：
5.5
通讯作者：
WRIGHT, P
中科院分区：
文献类型：
--
作者：
BRERETON, MG;WARD, IM;WRIGHT, P
给出了一系列线性聚乙烯样品的核磁共振测量结果，这些样品在一定的分子质量范围内具有低多分散性。总的来说，实验数据与前人的结果是一致的。本研究的主要目的是证明由于Brereton效应，横向弛豫函数可以用最新的理论模型精确地描述。这一理论是基于偶极相互作用的标度不变模型，该偶极相互作用是横向磁化弛豫的原因。它结合了一个相当一般的链动力学层次，可以用来在小的空间和时间尺度上适应Rouse模型，以及在更大的空间和时间尺度上适应各种其他模型，例如爬行模型。该模型解释了低多分散度的高相对分子质量样品的横向弛豫函数的复杂形状，表明这源于聚合物熔体的纠缠性质对分子迁移率的限制。
Results are presented for NMR measurements on a series of samples of linear polyethylene with low polydispersity over a range of molecular weights. In general terms, the experimental data are consistent with results of previous workers. The main thrust of the present investigation is to show that the transverse relaxation function can be accurately described by a recent theoretical model due to Brereton. This theory is based on a scale-invariant model of the dipolar interactions assumed responsible for the relaxation of transverse magnetization. It incorporates a rather general hierarchy of chain dynamics which can be used to accommodate the Rouse model at small space and time scales and a variety of other models, e.g., the reptation model, at larger space and time scales. The model is shown to account for the complex shape of the transverse relaxation function observed for high molecular weight samples of low polydispersity, showing that this has its origin in the restrictions on molecular mobility imposed by the entangled nature of the polymer melt.