本文探讨了具有稀疏至中等长链分支的聚乙烯的线性粘弹性行为。这类聚合物表现出一种共同的流变学特征，即在一定频率范围内损失角正切保持不变，并且储能模量和损耗模量遵循相同的频率指数进行缩放。这种看似幂律响应的现象与物理凝胶的行为相似，但其实是由两种部分重叠的终端松弛过程导致的。通过对全线性聚合物和双峰分子量分布聚合物的类似松弛行为的考虑，提出了一种量化长链分支程度的简单方法。
摘要：
We present new results and examine literature data concerning the linear viscoelastic behavior of polyethylene with sparse to intermediate levels of long-chain branching (LCB). These branched polymers displayed a common rheological signature, namely, a region of frequency-independent loss tangent along with the corequisite scaling of the storage and loss moduli to the same frequency exponent. This apparent power-law response occurred within a finite frequency window and bore resemblance to the behavior of physical gels. The appearance of this region, however, was the consequence of the presence of two distinct, yet partially overlapping, terminal relaxation processes. After considering the analogous relaxation behavior of wholly linear polymers with bimodal molecular weight distributions, we considered the polymers with LCB as blends of linear and branched species to develop a simple method of quantifying the extent of LCB. 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym
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